Note: Descriptions are shown in the official language in which they were submitted.
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Title: SYSTEM AND METHOD FOR READING POWER METERS
Field
[0001] Various embodiments described herein relate to a system and
method for reading power meters a housing for a power meter reader.
Background
[0002] Power meters are used by utility companies for measuring and
providing a readout for the quantity of electricity that has been used in a
commercial or residential establishment. Conventionally, if a person, such as
a homeowner, wanted to monitor energy consumption, then the person would
physically go outside to the location of the power meter to read the power
meter. This process is labor intensive, can be subject to human error and in
certain circumstances may not be safe for the person. Accordingly, there is a
movement towards automatic power meter readers that integrate the
capability of ineasuring the amount of electricity and communicating the
measurement to the utility company using either wired or wirefess signal
transmission. However, automatic power meter readers are generally limited
to newer power meter installations. Consequently, there is a need for a power
meter reader that can be retrofitted to the various types of existing power
meters.
[0003] Automatic power meter readers are typically retrofitted to
existing power meters and are typically connected to the power lines power to
obtain power. However, it would be more convenient to use one or more
batteries for a power source; i.e. the automatic power meter reader would be
easier to install since no connections to a power source would have to be
made. Unfortunately, the operations that are carried out by the automatic
power meter readers, such as detecting the rotation of the power meter disk
and transmitting information related to power consumption of the structure are
power hungry operations that would result in the frequent replacement of the
batteries. This is inefficient and cumbersome. Accordingly, it would be
advantageous to have a power meter reader that operates in an efficient
manner for prolonging battery lifetime.
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[0004] Another common issue for power utility companies is dealing
with unsatisfied consumers who complain about their high electric bills. What
is needed is technology that allows a consumer to know how much electricity
they are consuming, in dollars and cents or kilowatt-hours, and how much
their electric bill will be at the end of the month. The consumers can use the
feedback on the amount of electricity that they are using to reduce high
electric bills. There is also a growing pressure to increase energy
efficiency,
conserve energy resources and reduce atmospheric pollution. This can be
achieved with increased consumer awareness of the amount of energy that
they are consuming. In fact, studies show that energy savings of up to 15% or
more is possible when consumers get enough information to make meaningful
decisions about energy consumption.
[0005] In addition, there are various power meters currently on the
market including older style meters with dials and a rotary power disk, and
newer style meters with digital or other forms of output. The output may be
oriented at various directions such as facing outwards toward the face of the
power meter or facing outward towards the periphery of the power meter.
Summary
[0006] In one aspect, at least one embodiment described herein
provides an attachment means for attaching the detection unit to the power
meter unit. The attachment means is adapted for allowing the detection unit to
be attached to a wide variety of power meter units. In particular, the
attachment means includes a clamping means that is fitted around the
perimeter of the body of the power meter unit. The attachment means also
includes an arm that houses at least a portion of the sensor unit for sensing
the indication of power consumption of the power meter unit. The arm
includes an extension means for extending the length of the arm so that the
location of the sensors can be properly adjusted over an appropriate location
on the power meter unit. The arm may also include a pivot means for angling
the arm with respect to the main body of the detection unit.
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[0007] In yet another aspect, at least one embodiment described herein
provides a housing for a detection unit for automatically reading a power
meter unit mounted on a structure that is consuming power. The power meter
unit includes an indication with a cyclical property having a period that
varies
at a rate indicative of power consumption of the structure. The housing
comprises a main body for housing internal electronics; an extension member
connected to the main body, the extension member having a head region for
housing a sensor unit; and, an attachment means connected to the main body
for mounting the main body on the power meter unit.
[0008] In another aspect, at least one embodiment described herein
provides a housing for a detection unit that is used to read a power meter
unit
mounted on a structure that is consuming power. The power meter unit
including an indication with a cyclical property having a period that varies
at a
rate indicative of power consumption of the structure. The housing comprises
a main body for housing internal electronics; an extension member releasably
connected to the main body, the extension member having a head region for
housing at least a portion of the sensor unit; and an attachment means
connected to the main body for mounting the main body on the power meter.
The extension member can be connected to the main body in one of a
projected configuration, and a folded configuration to accommodate different
power meter units having difFerent locations for the indication.
[0009] In another aspect, at least one embodiment described herein
provides a housing for a detection unit that is used to read a power meter
unit
mounted on a structure that is consuming power, the power meter unit
including an indication with a cyclical property having a period that varies
at a
rate indicative of power consumption of the structure. The housing comprises
a main body for housing internal electronics; an extension member releasably
connected to the main body, the extension member having a head region for
housing at least a portion of the sensor unit; an attachment means connected
to the main body for mounting the main body on the power meter; means for
extending the location of the head region with respect to the main body;
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means for pivoting the location of the head region with respect to the main
body; and means for configuring the housing in a folded configuration for
directing the sensor unit towards the periphery of the power meter when the
indication is facing the periphery of the power meter.
Brief description of the drawinus
[0010] For a better understanding of the various embodiments
described herein and to show more clearly how it may be carried into effect,
reference will now be made, by way of example only, to the accompanying
drawings in which:
Figure 1 is a block diagram of an exemplary embodiment of a
power meter reader system;
Figure 2 is a block diagram of another exemplary embodiment of
a power meter reader system;
Figure 3a is a schematic of an exemplary embodiment of a
sensor unit that can be used in the power meter reader systems of Figures 1
and 2;
Figures 3b-3f are a series of illustrations of the operation of the
sensor unit of Figure 3a with respect to the motion of the black mark on the
power meter disk;
Figure 4 is shows a data structure that may be used for
transmitting data in the power meter reader systems of Figures 1 and 2;
Figure 5 is a front view of an exemplary physical embodiment of
a display unit that can be used with the power meter reader systems of
Figures 1 and 2;
Figure 6a is a front view of an exemplary physical embodiment
of a detection unit attached to a power meter that can be used with the power
meter reader systems of Figures 1 and 2;
Figure 6b is a perspective view of the detection unit of Figure
6a;
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Figure 6c is an exploded isometric view of the housing of a
portion of the detection unit of Figure 6a;
Figure 7 is a perspective view of a power meter showing
examples of different output locations for indicating power usage;
Figure 8a is a perspective view of an exemplary alternative
embodiment of a detection unit housing attached to a power meter in a
projected configuration;
Figure 8b is a front view of the detection unit of Figure 8a;
Figure 8c is a side view of the detection unit of Figure 8a;
Figure 9 is a front view of a detection unit of Figure 8a attached
to a power meter in a pivoted configuration;
Figure 10a is a perspective view of a detection unit of Figure 8a
attached to a power meter in a folded configuration;
Figure 10b is a front view of the detection unit of Figure 10a;
Figure 10c is a side view of the detection unit of Figure 10a;
Figure 11 is a perspective view of the detection unit housing of
Figure 8a in a folded configuration;
Figures 12a-12d are series of perspective views of the detection
unit of Figure 8a showing the steps of moving the position of the sensor unit
from a projected configuration to the folded configuration; and,
Figure 13 is an exploded view of the detection unit housing of
Figures 8a-8c.
Detailed description
[0011] In the following detailed description, numerous specific details
are set forth in order to provide a thorough understanding of the various
embodiments described herein. However, it will be understood by those of
ordinary skill in the art that these embodiments may be practiced without
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these specific details. In other instances, well-known methods, procedures
and components have not been described in detail so as not to obscure the
description of these embodiments.
[0012] Further, it will be appreciated that for simplicity and clarity of
illustration, elements shown in the figures have not necessarily been drawn to
scale. For example, the dimensions of some of the elements may be
exaggerated relative to other elements for clarity. Further, where considered
appropriate, reference numerals may be repeated among the figures to
indicate corresponding or analogous elements.
[0013] Referring first to Figure 1, shown therein is a block diagram of
an exemplary embodiment of a power meter reader system 10. The power
meter reader system 10 comprises a detection unit 12 and a display unit 14.
The detection unit 10 is mounted to a power meter unit 16 and the display unit
14 is mounted in a convenient location within the structure for which the
power meter unit 16 is monitoring power consumption. The detection unit 12
and the display unit 14 are preferably wirelessly coupled. However, the
detection unit 12 and the display unit 14 may be hardwired to each other in
known manner. The physical structure of the detection unit 12 and the manner
in which the detection unit 12 is mounted to the power meter unit 16 are
discussed in further detail below.
[0014] As is commonly known to those skilled in the art, the power
meter unit 16 is typically mounted on the outside wall of the structure for
which the power meter unit 16 is monitoring electrical power usage (the meter
unit 16 may also be on the inside of the structure). The power meter unit 16
has a clear plastic or glass cover for allowing the power usage to be read
while protecting the power meter unit 16 from the elements such as rain or
snow and against possible tampering. The power meter unit 16 also has a
power meter disk 18, shown schematically for illustrative purposes, which
rotates at a speed that indicates power usage. The power meter disk 18 is
oriented approximately perpendicular to the cover of the power meter unit 16
and has a black mark 20 that is in the shape of a small circular arc along the
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top and edge of the power meter disk 18. The power meter unit 16 also has a
plurality of dials (not shown) that indicate the current electrical power
usage of
the structure. The dials rotate in accordance with the rate of rotation of the
power meter disk 18.
[0015] It should be understood by those skilled in the art that the power
meter unit 16 may be a digital power meter unit with an alternative indication
of power consumption such as a digital representation of the power meter disk
18, or a vertical or horizontal bar on an LED or LCD Display with a mark that
moves across the display at the rate that the black mark on the power meter
disk revolves. Other representations are also possible. The black mark 20 on
the power meter disk 18 will hereafter be used in the description of the
operation of the power meter system for ease of description. However, it
should be understood that the black mark can generally be considered to be
an indication having a cyclical property that has a period with a varying rate
and that there are other types of power meters with other forms of indication
as described above.
[0016] The detection unit 12 comprises a sensor unit 22, a processing
unit 24, a temperature unit 26, a transmitter 28 and a power source 30. The
sensor unit 22 detects the rotation of the power meter disk 18 and provides a
consumption detection signal 32 to the processing unit 24 to indicate the
rotation frequency of the power meter disk 18. The sensor unit is described in
further detail below. The temperature unit 26 measures the outdoor
temperature and provides a temperature signal 34 to the processing unit 24.
[0017] The temperature unit 26 is optional. However, it is preferable to
include the temperature unit 26 for obtaining temperature information that can
be used by the power meter reader system for augmenting the power
consumption as is described in further detail below. The temperature unit 26
includes a temperature sensor, such as a thermistor, and a resistor used to
bias the temperature sensor (both not shown). The value of the resistor is
preferably chosen to draw the least amount of current possible while still
allowing the temperature sensor to provide a reading of the outside
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temperature. The temperature reading is a raw analog voltage level that is
dependent on the outside temperature. The raw analog voltage level is sent
by the transmitter 28 to the display unit 14 without any preprocessing. The
display unit 14 then converts the raw analog voltage level to a temperature
value. The display unit 14 performs the conversion to reduce the amount of
processing that is done by the processing unit 24 and hence reducing the
energy consumption of the detection unit 12.
[0018] The detection unit 12 includes one or more components for
reducing power consumption as is described in further detail below. For
instance, low voltage components are used to reduce power consumption.
Further, the operating parameters of the detection unit are chosen to reduce
power consumption. For instance, a low clock frequency, such as 32 kHz for
example, is used for the processing unit 24. In addition, the operating
voltage
of the sensor unit 22, the processing unit 24, the temperature unit 26, and
the
transmitter 28 is reduced. Further certain components of the detection unit
12,
such as the sensor unit 22, certain modules of the processing unit 24, and the
RF circuitry of the transmitter 28 are placed into sleep mode when not in use.
The sleep mode used for the sensor unit 22 is described in further detail
below.
[0019] The processing unit 24 uses the consumption detection signal
32 and the temperature signal 34 as well as other information, as is described
further below, for creating an information signal 36. The information signal
36
is sent to the transmitter 28 which generates and wirelessly transmits a
transmission signal 38 to the display unit 14. The transmitter 28 modulates
the
information signal 36 for transmission at a suitable transmission frequency.
The transmitter 28 is any suitable transmitter that has low current
consumption and the ability to operate in a sleep mode. The transmitter 28
also preferably provides error correcting codes for encoding the information
signal. Error correcting codes allows a certain amount of errors to be
introduced during transmission, yet these errors can be corrected at the
display unit 14. The benefit of such a transmission scheme is that the range
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for wireless transmission is increased for the same amount of power
consumption. Alternatively, the power consumption can be reduced while still
ensuring that the range for wireless transmission is sufficient. The
transmitter
28 also provides data for a CRC check that can be used by the display unit 14
to throw out corrupt messages. This is beneficial since, as the power of the
wireless transmission gets lower (i.e. the signal to noise ratio (SNR) gets
lower), it is more likely that the wireless transmission can become corrupted.
Since, reduced power consumption is a goal of the power meter reader
system 10, transmission is preferably done at a low SNR. Consequently error
correction codes and data for a CRC check is used to ensure that data is
correctly received by the display unit 14.
[0020] The power source 30 provides power for the operation of the
detection unit 12. The power source 30 is connected to the processing unit 24
which distributes the power to the remaining components of the detection unit
12. Preferably the power source 30 is a battery such as a 3.6V lithium AA
battery for example.
[0021] The sensor unit 22 is physically positioned adjacent to the power
meter disk 18 for detecting the rotation of the power meter disk 18. The
sensor unit 22 comprises an IR emitting diode and at least one photo diode
(described in more detail below). The IR emitting diode transmits a modulated
light beam to the surface of the power meter disk 18. The modulated light
beam is reflected by the power meter disk 18 at a certain level. However,
when the modulated light beam encounters the black mark 20, the light beam
is reflected at a lower level. Accordingly, the sensor unit 22 detects
revolutions of the black mark 20 based on a lower amount of reflected light
(this may also include the total absence of reflected light). The sensor unit
22
generates a pulse in the consumption detection signal 28 for each detection of
the revolution of the black mark 20. The modulated light beam is modulated at
a frequency of approximately 38 kHz so that sunlight can be filtered out by
the
sensor unit 22 (other suitable modulation frequencies may also be used). The
use of modulation also reduces the power that is required by the sensor unit
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22 since the modulation requires that the IR emitting diode is turned off for
very brief periods of time. To further reduce energy consumption, the sensor
unit 22 receives an enable control signal from the processing unit 24.
Accordingly, the sensor unit 22 is only operational for a portion of the
rotation
of the power meter disk 18 which coincides with the passage of the black
mark 20 past the sensor unit 22 (i.e. the sensor unit 22 is turned off until
the
black mark 20 is expected to return). This is described in more detail below.
[0022] The processing unit 24 controls the operation of the detection
unit 12 such that the detection unit 12 operates in an energy efficient
manner.
In the exemplary embodiment of Figure 1, the processing unit 24 includes a
control unit 42, a tracking unit 44, a prediction unit 46, a compression unit
48
and a memory unit 50 (some of these components may be omitted in other
embodiments as discussed further below). The control unit 42 directs the
operation of the detection unit 12 to enable the activation of the sensor unit
22, to generate power meter disk rotation information, read outdoor
temperature, generate packets of information to send to the display unit 14
and detect if the power source 30 is low. The processing unit 24 is
implemented by any suitable, ultra-low power microcontroller with associated
hardware and software.
[0023] The tracking unit 44 tracks the movement of the power meter
disk 18 based on the current speed and the maximum acceleration of the
power meter disk 18. The tracking unit 44 uses this information to dynamically
set a sleep period for the sensor unit 22. The sleep period is provided to the
control unit 42 each time the sleep period is updated. During the sleep
period,
the control unit 42 disables the operation of the sensor unit 22 via the
enable
control line 40 and enables the sensor unit 22 otherwise. The sleep period
can be based on an estimate of the return time of the black mark 20 for the
next revolution of the power meter disk 18. The return time of the power meter
disk 18 can be estimated based on the last two detections of the black mark
20. Alternatively, the last detected revolution of the power meter disk 18 can
be used to estimate the revolution rate of the power meter disk 18. For
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example, if the tracking unit 44 estimates that the last return time of the
meter
disk 18 took 2 seconds, then it is highly likely that the next cycle will be
somewhere close to that same time period.
[0024] The kinematics of the power meter disk 18 can also be used to
determine the minimum time required for the power meter disk 18 to make the
next full revolution. The sleep period can then be chosen accordingly. Based
on kinematics, the fastest revolution time for the power meter disk is given
by
equation 1:
tf = tcJ(1 +MAX_DELTA*tc/25920000) (1)
where tf is the fastest revolution time for the power meter disk 18, tc is the
last
time it took for one full revolution, MAX_DELTA is the value of watts
"kicking"
in during the next cycle (i.e. revolution of the power meter disk 18) and the
value 25920000 is a constant. The constant is calculated by multiplying the
kH factor of the power meter 16 (which is typically 7.2 Whr) with the amount
of
seconds in 1 hour and the constant 1000. The value of tc can be based on the
average or instantaneous revolution speed of the power meter disk 18. There
can be an array of values that can be used for MAX_DELTA. Some
exemplary numbers for MAX_DELTA include 2000, 5000 or 10000. The
particular value of MAX_DELTA that is used depends on the current
revolution speed of the power meter disk 18. If the disk 18 is revolving at a
slow speed, then a larger value of MAX_DELTA, such as 5000, can be
selected because there are many devices that can be turned on to increase
power consumption within the structure. However, if the disk 18 is revolving
at
a high speed, then a lower value of MAX_DELTA, such as 2000, can be
selected. This allows for the selection of a longer sleep period without
missing
the next revolution of the black mark 20. This is effective at high power
consumption levels associated with the structure (i.e. at fast revolution
speeds
for the power meter disk 18) since there aren't many more devices that can be
turned on, or turned on at a higher level, in the structure to consume more
energy and make the disk 18 revolve at a faster rate. However, at lower
revolution rates, the sleep period cannot be set as long using this method.
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[0025] In an alternative, the tracking unit 44 can set the sleep period
according to a percentage of the last full revolution time of the power meter
disk 18. For example, if the power meter disk 18 took 3 seconds for the last
revolution and a 50% sleep period is set by the tracking unit 44, then the
sensor unit 22 will sleep for 1.5 seconds after the last detection the black
mark 20 and then "wake-up" to detect the next occurrence of the black mark
20. This form of tracking is somewhat adaptive in nature. For example, if the
rotation of the power meter disk 18 slows down to 5 seconds per revolution,
the control unit 22 will change the sleep period to 2.5 seconds. However, if
the
rotation of the power meter disk 18 speeds up, there is a potential for cycles
to be missed. However, once the sensor unit 22 is turned back on it will
adjust
to the speed of the meter disk 18.
[0026] The percentage used to determine the sleep period can also be
changed depending on the speed of the power meter disk 18. For instance, if
the power meter disk 18 is rotating at a high speed, then the sleep period
percentage can be set to a higher value such as 90%, for example.
Alternatively, if the power meter disk 18 is rotating at a slower speed, then
the
sleep period percentage can be set to a lower value such as 50%, for
example. Accordingly, when the power meter disk 18 transitions from a low
revolution speed to a high revolution speed, a progressively higher sleep
period percentage can be used. The rationale behind this is that at high
rotation rates, the power meter disk 18 is unlikely to travel any faster since
most of the devices in the structure that consume energy are already turned
on which causes the power meter disk 18 to rotate at such a high rate. In this
case, it is extremely unlikely that the power meter disk 18 will rotate any
faster. Accordingly, setting a high sleep period in this case will most likely
not
result in any missed detections of the black mark 20. Alternatively, when the
power meter disk 18 is rotating at a slow rate, it is quite likely that the
power
meter disk 18 can speed up quite quickly. Firstly, the inertia of the power
meter disk 18 is low so that the power meter disk 18 can change speeds
quickly. Secondly, and more importantly, since the power meter disk 18 is
rotating at a slow speed, there are many devices that can be turned on, or
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alternatively turned on at a higher setting, which increases power
consumption and therefore the speed of the power meter disk 18. This is even
more pronounced depending on the time of day, when it is more likely that
devices are turned on and off. Therefore, at low speeds, to avoid missing
detections of the black mark 20, the sleep period is typically set to a lower
percentage of the cycle time of the power meter disk 18.
[0027] Furthermore, in either a periodic or aperiodic fashion, the sensor
unit 22 does not enter sleep mode during a complete rotation of the power
meter disk 18, so that the sensor unit 22 can avoid becoming out of sync with
the rotation of the power meter disk 18. For example, if a rotation of the
power
meter disk 18 is missed, the sensor unit 22 will not be aware of this and will
assume that the revolution time of the power meter disk 18 is longer than it
actually is and will add the extra time to the current revolution cycle. This
may
cause the sensor unit 22 to miss successive cycles. To avoid this, full cycle
detection can be used at various times during the operation of the detection
unit 12.
[0028] In another alternative, the tracking unit 44 can adjust the sleep
period based on the time of day since the amount of power consumption, and
hence the rotation speed of the power meter disk 18, can vary depending on
the time of day. For instance, power consumption may decrease at night, and
it also very unlikely that additional devices will turn on at night, so the
sleep
period can be set to a larger percentage of the rotation speed of the power
meter disk 18 at night. In another alternative, the sleep period can be based
on the last X(e.g. 100) revolution times for the power meter disk 18.
[0029] In another alternative, the tracking unit 44 can adjust the sleep
period based on the amount of energy remaining in the power source 30. For
instance, if the power source 30 is a battery and the control unit 42 detects
a
low amount of power remaining in the battery, then the sleep period can be
extended to conserve power consumption by the detection unit 12 at the cost
of reduced accuracy of counting the number of rotations of the power meter
disk 18.
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[0030] In each of the above cases, the tracking unit 44 also sets upper
and lower limits for the sleep period. An upper sleep period limit is set so
that
the sensor unit 22 will not miss the detection of too many cycles should the
rotation of the power meter disk 18 go from a very slow speed to a very high
speed before the sensor unit 22 wakes up. The upper sleep period limit is set
to be approximately half the minimum time the black mark 20 is in view of the
sensor unit 22. This is based on the Nyquist rate for sampling the black mark
20 on the power meter disk 18 and ensures that the sensor unit 22 will be on
often enough to detect the black mark 20 even for the fastest speed at which
the power meter disk 18 can rotate. This limit is capped at approximately 90-
95% of the revolution time for the power meter disk 18. Conversely, the lower
sleep period percentage, which is used at low revolution speeds of the power
meter disk 18, is set based on the fact that it is known that the power meter
disk 18 can go much faster as there are more loads that are available to
consume power and hence increase the rotational speed of the power meter
disk 18. This limit is capped at approximately 50%.
[0031] The prediction unit 44 is used to alter the rate at which the
transmitter sends the transmission signal 38 to the display unit 14.
Accordingly, the data sent to the display unit 14 is not necessarily sent at a
periodic rate. Rather, the prediction unit 44 uses prediction techniques to
generate parameters for a prediction model that predicts the revolution of the
power meter disk 18. The values of the model parameters are sent to the
display unit 14 and the display unit 14 uses the values of the prediction
model
parameters to "simulate" the rotation of the power meter disk 18 and calcuiate
future values of power usage in real-time. In particular, depending on the
accuracy of the prediction model, the values of power usage are updated by
the display unit 14 at the same rate that the power meter disk 18 is actually
rotating. The usage of prediction model parameters advantageously allows
the display unit 14 to show the current power consumption without the
detection unit 12 using up the power source 30 by sending frequent
transmissions to the display unit 14. Accordingly, the detection unit 12
reduces energy consumption since transmission occurs less often. However,
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it appears as if the display unit 14 is receiving a steady stream of data,
since
the display unit 14 is providing power consumption data of the structure in
real-time, even though the data transmissions from the detection unit 12 are
not periodic. Also, it should be understood that when each data transmission
is received, the display unit becomes synchronized with the real number of
cycles that have occurred since this information is provided by the detection
unit 12. Another advantage of using a prediction model, is that the values of
the prediction model parameters are transmitted rather than the actual data;
this reduces the amount of data that is transmitted to the display unit 14
which
also reduces the power consumption of the detection unit 12.
[0032] The values for the model parameters that are sent to the display
unit 14 are updated when the model becomes out of sync with the readings
taken by the sensor unit 22. For instance, when the prediction unit 46
determines that the prediction model has a prediction error epred that is
greater
than a predetermined prediction error threshold, such as 1 kWh for example,
the prediction unit 46 recalculates values for the prediction model
parameters,
based on the latest values of the consumption detection signal 32. The
updated values of the prediction model parameters are then sent to the
display unit 14. The prediction unit 46 can also set a minimum and maximum
time period between transmissions so that the detection unit 12 does not send
too many transmissions to the display unit 14 while at the same time
communicating at a basic rate to let the display unit 14 know that the
detection unit 12 is still operational. Exemplary minimum and maximum time
limits for sending transmissions are 3 minutes and 20 minutes respectively.
The efFect of the minimal time period for transmissions can also be
implemented by setting the prediction error low enough so that the prediction
error may be violated in a short period of time.
[0033] The complexity and accuracy of the prediction model is based
on the computing power of the processing unit 24, the type of prediction
algorithm being used, the amount of data from the consumption detection
signal 32 that is used for prediction, and the determinism of the data in the
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consumption detection signal 32. The complexity and accuracy of the
prediction model is also governed by the amount of power that must be
expended by the detection unit 12 while employing the prediction model; it is
desirable for the power consumption of the detection unit 12 to be as low as
possible. An example of a prediction model that can be used by the prediction
unit 46 is given by equation 2:
s [n] = s[n - n,pg ] + n,pg = v (2)
where s is the predicted power consumption in the structure, s is the actual
power consumption in the structure, v is the velocity of the power meter disk
18 (based on the last k values of s), n is the current data index and n,a9 is
the
number of index points into the prediction. The velocity (i.e. rotational
speed)
is inversely proportional to the last revolution time of the power meter disk
18
and therefore proportional to the power consumption of the structure. In this
sense, the velocity is the average velocity of the power meter disk 18. The
velocity could also be based on the instantaneous velocity of the power meter
disk 18 according to the equation 1 which is based on kinematics. The index n
is in terms of discrete time. For example, for each interval of n, 3 seconds
may have expired. For instance, n= 1 means 3 seconds have passed.. The
value s[n-nla9] represents the last known power consumption value before the
current version of prediction began. Accordingly, the prediction parameters
that are transmitted for this prediction model are the absolute cycle count
and
the time for the last revolution.
[0034] The prediction model also employs a prediction error that is
used to recalculate values for the parameters of the prediction model when
the prediction error of the prediction model exceeds a certain level, such as,
for example, spred = 200 cycles or equivalently 10 cents based on a kh factor
of 7.2 Whr and an energy rate of 7 cents per kWh. Other suitable examples of
prediction model errors include spred = 20 cycles (i.e. 1 cent) or 100 cycles
(i.e.
5 cents).
CA 02602867 2007-09-18
-17-
[0035] The prediction model shown in equation 2 is referred to as a
LAST prediction model since it is based on the velocity of the power meter
disk 18 in the latest revolution. Another example for a prediction model that
can be used is referred to as a LINEAR prediction model. Although the LAST
prediction model is linear in that it uses the latest speed of the power meter
disk 18 as the velocity, the LINEAR prediction model uses the difference in
cycle count between successive transmissions of data and the elapsed time
between the transmissions from the transmitter to calculate the velocity. The
remainder of the LINEAR prediction model operates in the same fashion as
the LAST prediction model.
[0036] Other classes of prediction models may also be used such as
AR, MA, or ARMA models. Kalman filtering or other forms of tracking may
also be used. Simple, nonlinear prediction models may also be used.
However, it is preferable to use a prediction model that has low computational
complexity for reducing the power consumption of the detection unit 12. This
means that the order of the prediction model is high enough to give accurate
results but low enough to avoid undue amounts of computational complexity.
[0037] The control unit 42 generates information for transmission. In
one embodiment, the generated information includes:
a) the time in milliseconds that it took for the last revolution of
the power meter disk 18;
b) the cycle count (i.e. the number of revolutions of the power
meter disk 18 that have been counted by the detection unit 12);
c) the voltage status of the power source 30;
d) the outside temperature;
e) a device address (the transmitter 28 has a unique address);
and,
f) cyclic redundancy check (CRC) data.
CA 02602867 2007-09-18
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-18-
The model parameters that are sent from the detection unit 12 to the display
unit 14 depend on the particular prediction model that is being used. One
option is to base the prediction models on the cycle count, and the latest
revolution time of the power meter disk 18 according to equation 2. The
values for these parameters are given in elements a and b above. In this
particular example, the display unit 14 can synchronize the displayed cycle
count with the cycle count that is transmitted by the detection unit 12. The
display unit 14 can then use the cycle count and the latest revolution time to
predict future cycle counts until the next transmission is received. If on the
next transmission, the display unit 14 has "over-predicted" and is displaying
a
higher consumption rate than the real corresponding cycle count, then one
option is to not update the display unit 14 until the real energy consumption
value "catches-up" to the predicted value. This is to prevent the display unit
14 from showing a lower consumption value after it had previously displayed a
higher consumption value. If however the power meter disk 18 speeds up,
then on the next data transmission, the display unit 14 will display a sudden
"jump" in energy consumption.
[0038] The compression unit 48 receives the generated information and
compresses this information to provide the information signal 36 which is then
transmitted by the transmitter 28. The compression reduces the length of the
generated information. As a result, the transmitter 28 does not expend as
much energy in transmitting the information signal 36. This is beneficial
since
wireless communication can be a key cause of energy dissipation. However,
there must be an acceptable balance between a reduction in the amount of
data that is transmitted for reducing energy consumption and an acceptable
level of information loss that is introduced by compression.
[0039] Alternatively, the compression unit 48 can be used to compress
the raw data in the consumption detection signal 32 or a series of values for
the prediction model parameters that have been calculated over a given time
period. This is beneficial in the case where data transmissions from the
detection unit 12 to the display unit 14 are not that frequent. This situation
can
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arise when a consumer does not want real-time feedback but wants to review
the energy consumption once a day or possibly once a week. In this case, the
information provides resolution between successive data transmissions; i.e.
the consumer can get an idea of the average energy consumption between
successive data transmissions, however, by transmitting more information,
the consumer can get an idea of what happened in energy consumption
between the two transmission times and may see transient increases or
decreases in energy consumption of the structure.
[0040] The compression unit 48 uses a compression method that is
easy to compute using a standard low powered microcontroller. Any
compression method that exceeds the memory capacity of the memory unit
50, the time between scheduled updates to the display unit 14, or the power
to transmit the data is not efFective. It should also be noted that if too
much
data is compressed and the message sent containing the information is lost or
corrupted then there is no way to recover the data without resending the data.
However, limitations of the memory unit 50 may prevent the resending of
data. Further, the estimation of the power consumption due to the
compression method is based on the number of bits needed to represent the
compressed time series. The fewer the number of bits needed to represent
the compressed time series, the less power required to transmit the same
amount of information.
[0041] Several compression methods can be used to compress a time
series such as, but not limited to, Wavelets, Fourier Transforms, Piecewise
Linear Approximations and polynomials. In addition, once a compression
method is selected, an acceptable compression error Ecomp is preferably
specified. The compression error Ecomp represents the amount of information
that can be reasonably lost due to compression. This allows the algorithm to
compress the data such that when it is uncompressed the values are within
Ecomp of the original data values. Once set, the prediction error Ecomp may be
dynamically changed. However, it is preferable that the dynamic value of the
prediction error never exceed the originally set Ecomp because this value
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specifies the maximum allowable error. In general, the greater the Ecomp the
higher the compression rate that can be achieved and thus a greater
reduction in power consumption.
[0042] In this case, the data to be compressed is power consumption
data which is a time series x[n] that has a plurality of data elements in
which
the index n is a time index and the values associated with a time index is the
current demand. if the data series is graphed, the area under is the graph is
the power consumption. The demand can be calculated by multiplying the kH
factor of the power meter unit 16 with the constant 3600 and dividing by the
latest revolution time of the power meter disk 18 that is associated with the
current time index. The success of a compression technique depends on the
presence of an underlying deterministic process in the time series x[n]. An
example of a compression algorithm is the following. The compression error
Ecomp defines a maximum error in the compression algorithm. The algorithm
begins with taking the first two raw data points without compression. These
two data points are successive absolute cycle counts and the times at which
they occur. From this a revolution time can be calculated (alternatively the
kinematic equation can be used for the revolution time) and the demand is
calculated as explained above. The demand and the time index is added to
the compressed data series. The next demand point is repeatedly calculated
and only added to the compressed data series if the absolute value of the
magnitude of the demand point minus the magnitude of the previous demand
point in the compressed data series is larger than the prediction error Ecomp.
If
the absolute value of the difference is larger than the magnitude of the
demand point and the corresponding time index is added to the compressed
data series. This procedure continues until there are no more data points to
compress. It should be understood that rather than save the demand value,
the corresponding revolution time can be saved instead since these values
are related to one another by a factor. In another alternative, the absolute
cycle count at the time index may also be saved in the compressed data
series. Also, rather than saving the value of the demand or revolution time,
CA 02602867 2007-09-18
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the delta (i.e. difference between the current demand or revolution time and
the previous value) can be saved. The compression ratio (CR) that can be
achieved is represented by equation 3:
CR = K(bs + b,p ) (3)
nbs
where K is the compressed sequence length; bs is the size of the sample in
terms of bits; btp is the size of the time index in terms of bits and n is the
number of samples in the original time series prior to compression which
represents the number of times that the rate of rotation of the power meter
disk 18 is checked. The memory unit 50 is memory that is associated with the
processing unit 12. The memory unit 50 is preferably an EEPROM. However,
depending on the implementation of the processing unit 24, the memory unit
50 may be RAM or another suitable memory device that has low power
consumption. The memory unit 50 is used to save important parameters that
are needed for the operation of the detection unit 12 and that can not be lost
should power to the detection unit 12 be removed. For instance, the memory
unit 50 can save instructional code that the control unit 42 uses to control
the
operation of the detection unit 12. The memory unit 50 is also preferably used
to save the absolute cycle count.
[0043] The tracking unit 44, prediction unit 46 and compression unit 48
operate independently of each other. Accordingly, alternative embodiments of
the detection unit 12 can incorporate one or more of these units and it is not
necessary that the detection unit 12 contain each of these units. However, the
greatest amount of reduction in energy consumption for the detection unit 12
is achieved when the detection unit 12 contains all of these units. However,
if
both compression and prediction are used, if the compression error Ecomp Is
equal to the prediction error Epred, then there is no benefit to compression
because the values of the prediction model parameters will be updated often
enough to allow the display unit 14 to construct the same representation of
the data that compression would have constructed. It is therefore necessary
to set the prediction error Epred higher than the compression error Scomp=
CA 02602867 2007-09-18
-22-
Effectively, this means that data for a certain amount of time (Tc) is
compressed and that the data is transmitted every (Tp) seconds due to the
amount of prediction error that is tolerated and that Tp is greater than Tc
(i.e.
having a larger prediction error allows one to use the same values for the
prediction model parameters for a longer period of time, since over time the
prediction error will accumulate).
[0044] The display unit 14 comprises a receiver 52, a display
processing unit 54, a real-time clock 56, a receiver memory unit 58, a display
60, an interface unit 62, a buzzer unit 64 and an appliance control unit 68.
Some of these elements may be optional such as the buzzer unit 64, the
appliance control unit 68 and the real-time clock 56 if another means can be
obtained to provide time. The display unit 14 may be plugged into a wall
receptacle to receive power from the mains supply or the display unit 14 may
have an internal power source such as a battery (not shown) that is
connected in known manner.
[0045] The receiver 52 receives the transmission signal 38, performs
the necessary demodulation and pre-processing, as is commonly known to
those skilled in the art, and generates a received signal 66 that is similar
to
the information signal 36. Data will typically be sent in data packets in the
transmission signal 38. During the generation of the received signal 66, the
receiver 52 checks the device address data in the received data packets to
ensure that the transmission signal 38 was received from the appropriate
transmitter 28 and not from a transmitter of a different power meter reader
system. If the receiver 52 determines that the transmission signal 38 was
provided by the transmitter 28 of a different power meter reader system, then
the receiver 52 will discard the received data packets. The receiver 52 also
checks the CRC data in the data packets of the transmission signal 38 to
make sure that data integrity is maintained during transmission. If a
discrepancy is found in the CRC data, there is an error in the data packets of
the transmission signal 38 and the receiver 52 discards these data packets.
Further, continuously "listening" for the transmission signal 38 is power
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-23-
consuming. Accordingly, the transmitter 28 and the receiver 50 preferably
employ unidirectional communication from the transmitter 28 to the receiver
52.
[0046] The receiver 52 provides the received signal 66 to the display
processing unit 54 for further processing. The display processing unit 54
extracts the time for the last revolution of the disk and the cycle count, and
uses the same prediction model that was used by the prediction unit 46 (if
prediction is employed) to display the instantaneous demand in Wh or kWh or
$/hr (rather than dollars another appropriate form of currency can be used
depending on the country in which the power meter reader system is being
used). The display processing unit 54 also uses this information to display a
disk on the display 60 that spins at the same rate as the power meter disk 18.
The display processing unit 54 also extracts the power source voltage status
information and the temperature reading to display this information on the
display 60. If the power source voltage is low, then the display processing
unit
54 will display a battery low symbol on the display 60.
[0047] The display processing unit 54 uses the prediction model
parameters to predict the amount of energy consumption that occurs until the
next data transmission from the detection unit 12. In one example, the
detection unit 12 sends over the absolute cycle count (which is never reset in
the detection unit 12) and the last revolution time. The receiver uses these
two values to predict the occurrence of successive revolutions of the power
meter disk 18.
[0048] The display processing unit 54 can also allow the consumer to
predict energy consumption for a specified time into the future, and also has
the ability to store a history of energy consumption in the memory unit 56.
Accordingly, the display processing unit 54 employs prediction on a longer
time scale to allow the consumer to predict energy consumption for the next
billing cycle (i.e. 30 days) for example (a similar prediction model can be
used
as those previously described except with a longer time period). The long
term prediction (i.e. long-range bill prediction) can use linear regression
based
CA 02602867 2007-09-18
-24-
on the energy consumption in the last several days (i.e. the energy
consumption is saved daily by the display unit 14) to predict the amount of
the
future energy bill.
[0049] The display processing unit 54 can also use the revolution count
information to display the amount of greenhouse gas that the structure, which
consumes the power, is responsible for emitting. This calculation is based on
the region in which the structure is located since it is based on carbon-
dioxide
emission rates which are specific for a particular region or utility company.
In
particular, the display processing unit 54 can show the amount of carbon-
dioxide that has been emitted in terms of tones, pounds or kilograms.
Alternatively, the display processing unit 54 can display environmental
credits/token/units that have been accumulated, used or that are remaining.
These tokens may be distributed by the government or an environmental
agency. The display processing unit 54 may also display a warning signal to
notify the user of excess consumption; this may include but is not limited to
a
graphic on the display 60 such as a smoke stack, a sad face and/or a beep
provided by the buzzer unit 64. The carbon-dioxide emission rates based on
the province, state and/or country in which the power meter reader system 10
is used can be pre-programmed into the display processing unit 54. The
consumer can then simply select their location on the display unit 14.
[0050] The real-time clock 56 is used to maintain time in the display
unit 14. The time is received by the display processing unit 54 for computing
the current time and displayed on the display 60. The time is also used by the
display processing unit 54 in conjunction with Time of Use Energy Rates. For
instance, depending on the particular utility company, the consumer may be
charged difFerent rates for energy consumption depending on the time of day
when the energy is consumed. This is done to reduce energy consumption at
peak times. For example, between 5 PM and 8 PM. a utility company may
charge 10 cents/kWh rather than 6 cents/kWh so that the consumer reduces
energy consumption between 5 and 8 PM.
CA 02602867 2007-09-18
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[0051] The memory unit 58 can be any suitable memory device such as
an EEPROM. The memory unit 58 is used to store critical information so that
the display unit 14 can be powered down and powered back up without losing
important information. Examples of critical information include different
rates
for energy consumption based on location, the cumulative energy consumed,
the number of days to use for long-range bill prediction, etc.
[0052] The display unit 60 can be any suitable display device such as
an LCD. The display unit 60 is used to display time and date information,
power consumption in dollar amounts (or other currency), or other
consumption units such as kWh, carbon-dioxide emission levels, and a disk
that spins at the same rate as the power meter disk 18 as well as other
information. The display unit 60 is described further below in an exemplary
embodiment.
[0053] The interface unit 62 can be a keypad or similar device which
allows the user to enter information into the display unit 14 or to choose
between various modes of operation. The buzzer unit 64 provides an audible
sound to provide various information to the consumer. For instance, the
buzzer unit 64 may sound an alarm when the voltage level of the power
source 30 of the detection unit 12 is running low. The buzzer unit 64 can also
provide a sound to verify that the consumer has depressed a key on the
interface unit 62. Any suitable buzzer can be used.
[0054] The appliance control unit 68 can be used in conjunction with
the information that is provided by the detection unit 12 to direct the
operation
of appliances within the structure for which energy consumption is being
monitored. The appliance control unit 68 is connected to the structure's
powerline to send appliance control signals to the appliances via a powerline
communications device. Any suitable powerline communications device can
be used such as the X10T"" or CEBUST"" powerline devices. The appliances
have a corresponding receiver module with a unique address. Accordingly,
the appliance control unit 68 can send specific control instructions to a
particular appliance. These control instructions can direct the appliance to
turn
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on, turn off, to increase an operational setting or decrease an operational
setting. For example, the appliance can be an air conditioner and a control
instruction may be to decrease the amount of cold air provided by the air
conditioner.
[0055] In use, the appliance control unit 68 receives at least one of
temperature information, energy consumption information and time
information from the display processing unit 54 and uses this information to
control an appliance. For instance, based on temperature information, and
depending on the season and the particular temperature, the appliance
control unit 68 can instruct a heating or cooling appliance to increase or
decrease its operational setting. Alternatively, based on energy consumption,
the appliance control unit 68 may instruct several appliances to turn off to
conserve energy if the current level of energy consumption is too high. In
another alternative, based on the time of day, the appliance control unit 68
can instruct one or more appliances to turn off. For instance, some utilities
charge a higher rate during peak periods to encourage consumers to
consume less energy. During these times periods, the appliance control unit
68 can instruct some of the more power hungry appliances to turn off. Of
course, these instructions are within reason; i.e. it is not reasonable to
turn off
a fridge since the contents within the fridge may spoil. Rather than having
the
appliances turn off, the appliance control unit 68 can alter the operation
level
of the appliances.
[0056] Referring now to Figure 2, shown therein is a block diagram of
another exemplary embodiment of a power meter reader system 10' with an
alternative display unit 14'. In this case, the display unit 14' includes a
communication unit 70 for communicating with a computing device such as a
PC 72. The communication unit 70 can be an RS232 data interface, a USB
port or any other suitable communication device. The PC 72 can be
connected to the display unit 14' and runs a utility software program 74 to
interact with the receiver 52. The software on the PC 72 can be used to
upload the history of energy consumption from the display unit 14' so that the
CA 02602867 2007-09-18
' -27-
consumer can make graphs, etc. to determine when the most energy is being
consumed. It should be understood by those skilled in the art that another
appropriate computing device can be used rather than a PC.
[0057] The consumer can also use the PC 72 to connect with a website
provided by a utility web server 76 over the internet 78. The consumer may
browse the web site to view utility rates, view consumption patterns and get
energy saving hints and green house gas information. The utility web server
76 would obtain this information from an associated utility database 80. The
consumer can also download carbon-dioxide information from the website and
provide this information to the utility software program 74 which then passes
this information to the display unit 14'.
[0058] Referring now to Figure 3a, shown therein is an exemplary
embodiment of a sensor unit 100 that can be used with both of the power
meter reader systems 10 and 10'. The sensor unit 100 comprises an emitter
102, a first detector 104 and a second detector 106. In this embodiment, two
detectors are used to make the sensor unit 100 more robust to false
detections as well as ambient light. Furthermore, in this embodiment, the
sensor unit 100 receives a polling signal 108 from the control unit 42 as well
as the enable control signal 40. The sensor unit 100 also provides first and
second detection signals 110 and 112 that are combined to form the
consumption detection signal 32. In terms of physical layout, the emitter 102
is located between the first detector 104 and the second detector 106 (this is
illustrated in Figures 3b-3f and discussed in more detail below).
[0059] The enable control signal 40 is combined with the VCC power
supply signal in a logical AND operation by the AND gate 114. Accordingly,
when the enable control signal 40 is high, the VCC power supply signal is
provided to the remainder of the circuitry of the sensor unit 100 thereby
enabling the sensor unit 100. Otherwise, the sensor unit 100 is in sleep mode
with no power consumption. Alternatively, rather than having the AND gate
114, other suitable devices may be used such as a CMOS transistor or a
CA 02602867 2007-09-18
-28-
more complex transmission gate. It should be understood that capacitors to
ground can be connected in parallel with VCC to remove noise.
[0060] In an alternative, the AND gate 114 can be replaced by a
transmission gate; i.e. a CMOS transistor for example, can be used.
Alternatively, the VCC power supply signal can be provided by a pin on a
microcontroller if a microcontroller is used to implement the control unit 42
and a sufFicient amount of current can be provided by the pin.
[0061] In this exemplary embodiment, the emitter 102 comprises a light
emitting diode (LED) D1 connected in series with a resistor R1 and a
transistor Q1. The resistor R1 is connected to the output of the AND gates
114 and to a first node of the LED D1. The other node of the LED D1 is
connected to the collector of the transistor Q1 and the emitter of the
transistor
Q1 is connected to ground. The base of the transistor Q1 is connected to a
first node of a resistor R2. The other node of the resistor R2 is connected to
the polling signal 108. In use, when the sensor unit 100 is enabled and the
polling signal 108 is pulsed high, the transistor Q1 is turned on and conducts
current which allows the LED D1 to emit light. The LED D1 is selected such
that it emits infrared light. The LED D1 may emit modulated IR light at a
frequency of 38 kHz for example although other modulation frequencies may
be used such as 2 kHz for example. The detection signals 110 and 112 are
then filtered by a bandpass filter that has a passband that matches the
modulation frequency used to emit the IR light. The bandpass filtering can be
done in hardware (not shown) or via software by a unit within the processing
unit 24.
[0062] The first detector 104 and the second detector 106 are
preferably implemented to have the same structure so that the first and
second detection signals 110 and 112 are similar to one another. Accordingly,
only the first detector 104 will be described. The first detector 104
comprises a
photodiode D3 connected in series with a resistor R6. A first node of the
photodiode D3 is connected to the output of the AND gate 114 and a second
node of the photodiode D3 is connected to the resistor R6. The other node of
CA 02602867 2007-09-18
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the resistor is connected to ground. The series combination of the photodiode
D3 and the resistor R6 is connected in parallel with a series combination of a
resistor R4 and a transistor Q3. A first node of the resistor R4 is connected
to
the output of the AND gate 114 and a second node of the resistor R3 is
connected to the collector of the transistor Q3. The base of the transistor Q3
is connected to the second node of the photodiode D3. The emitter of the
transistor Q3 is connected to ground.
[0063] In use, when the sensor unit 100 is enabled and the polling
signal 108 is pulsed high, the LED D1 emits IR light that is reflected by the
shiny surface of the power meter disk 18. In this case, the black mark 20 has
not come into the vicinity of the LED D1 or the photodiode D3. Accordingly,
the photodiode D3 is conducting, the transistor Q3 is turned on and current
flows through resistor R4. Accordingly, there is a voltage drop across the
resistor R4 and the voltage at the emitter of the transistor Q3 is relatively
constant and has a low magnitude with respect to the power supply voltage
VCC. However, when the LED D1 shines IR light on the black mark 20, not as
much energy is reflected by the power meter disk 18. Consequently, the
photodiode D3 turns off, no current flows through the resistor R6 and the
transistor Q3 turns off. Accordingly, only a small amount of current flows
through the resistor R4 and a high voltage with respect to the power supply
voltage VCC is seen at the emitter of the transistor Q3 and hence in the first
detection signal 110.
[0064] Referring now to Figures 3b-3f, shown therein is an illustration of
the operation of the sensor unit 100. The LED D1 and the photodiodes D2
and D3 are oriented with the photodiodes D2 and D3 on either side of the
LED D1. These elements are spaced according to the angular extent of the
black mark 20 which is typically 5 degrees or so. In one exemplary
embodiment, these elements are separated by approximately 3 or 4 mm. This
spacing is also chosen to ensure that reflections from small black specks on
the power meter disk 18 will not trigger both photodiodes. In addition, these
elements have a plastic shield between them so that light from the LED D1
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-30-
does not go directly to either photodiode D2 or D3. Further, the voltage from
each photodiode D2 and D3 can be subtracted from one another to cancel out
any common mode voltage caused by IR going directly to the photodiodes.
[0065] Figure 3b includes a series of panels that depict the different
cases for the location of the black mark 20 on the power meter disk 18 with
respect to the location of the emitter 102 and the first and second detectors
104 and 106. These five cases are represented by a state machine with five
corresponding states. The state machine is implemented in the control unit
42. Figure 3b shows the case where the black mark 20 has yet to reach the
emitter 102 and the first and second detectors 104 and 106. In this case, the
output of the first and second detectors is a low logic level (i.e. 0). Figure
3c
shows the case where the black mark 20 is close to the emitter 102 and the
first detector 104 but not the second detector 106. Consequently, the output
of
the first detector 104 is a high logic level (i.e. 1) and the output of the
second
detector 106 is a low logic level. Figure 3d shows the case where the black
mark 20 is close to the emitter 102 and the first and second detectors 104 and
106. In this case, the outputs of the first detector 104 and the second
detector
106 are both a high logic level. Figure 3e shows the case where the black
mark 20 is close to the emitter 102 and the second detector 106 but not the
first detector 104. In this case, the output of the first detector 104 is a
low logic
level and the output of the second detector 106 is a high logic level. Figure
3f
shows the last case in which the black mark 20 is far from the emitter 102 and
the first and second detectors 104 and 106. In this case, the outputs of the
first and second detectors 104 and 106 are both low logic levels. Accordingly,
based on the outputs of the first and second detectors 104 and 106, the
passage of the black mark 20 can be detected. In particular, the consumption
detection signal 32 can be based on the logical AND of the first and second
detection signals 110 and 112.
[0066] The use of two detectors allows for more robust operation of the
sensor unit 100 and less false detections. For instance, there may be spurious
detections by either the first detector 104 or the second detector 106 which
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may be due to dirt on the power meter disk 18 and the like. However, it is
very
unlikely that both detectors 104 and 106 will give a spurious detection at the
same time. Furthermore, it is very unlikely that noise will trigger a
detection if
one requires that all five states happen sequentially before making a
detection
of the passage of the black mark 20 by the sensor unit 100.
[0067] In an alternative, the five states can be reduced to three states
by subtracting the first and second detection signals 110 and 112 from one
another and noting the change in sign in the subtraction signal. For instance,
the subtraction result for each of the five states, beginning with the first
state
and moving sequentially to the last state and subtracting the second detection
signal 112 from the first detection signal 110, is 0, 1, 0, -1 and 0.
Accordingly,
the transition from 1 to 0 to -1 signifies the passage of the black mark 20
past
the sensor unit 100 and makes it very unlikely that glitches or noise will
result
in a false detection.
[0068] Referring now to Figure 4, shown therein is an example of a
general transmission data structure 120 that may be used for transmitting
data in either of the power meter reader systems 10 and 10'. This
transmission protocol can be useful when the display unit is configured to
interact with more than one detection unit (i.e. monitor the energy
consumption of more than one structure) wherein each detection unit can
operate in a different manner. In addition, other transmission data structures
may be used that only have a portion of the fields contained in the
transmission data structure 120. AII efforts have been made to reduce the
complexity and overhead of the transmission data structure 120 to reduce
energy consumption in the detection unit 12. The transmission data structure
120 will not be effective if the overhead to transmit the data is greater than
the
data itself. The numerals 7 through 0 at the top of Figure 4 signify the
number
of bits that are used to make up a particular piece of information in the
transmission data structure 120.
[0069] The transmission data structure 120 comprises a battery level
field 122, a battery voltage field 124, a listen policy field 126, a listen
period
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field 128, an E_compression field 130, an E_prediction field 132, a history
length 134, a first history length field 136, a second history length field
138, a
compressed history data field 140, a first current value field 142, a second
current value field 144, a prediction model field 146, a first model
parameters
field 148 and a second model parameters field 150. The battery level field 122
is sent for all transmissions made to the display unit 14. The battery level
can
be used to warn the end user of the display unit 14 that the detection unit 12
is getting low on power. Although some batteries have a sharp voltage drop
curve as battery power dissipates, most batteries will give fair warning that
they are getting low on power. The battery level field 122 is composed of 5
bits allowing for 32 distinctive levels of the battery voltage based on a
linear
scale.
[0070] The battery voltage field 124 shows an initial battery voltage for
the power source 30. The initial battery voltage can be represented by eight
values (i.e. 3 bits provide 000 sequentially through to 111). As an example,
the following voltage levels can be represented: 1.2V, 1.5V, 2V, 2.4V, 3V,
3.6V, 4V and 6V. The initial battery voltage may also be coded in the display
processing unit 54 since it is quite likely that the size of the battery used
with
the detection unit 12 is known a priori. However, there may be several
different styles of detection units 12 that can use different size batteries.
[0071] The listen policy field 126 indicates to the display unit 14 when
to listen for messages from the detection unit 12. In an unpredictable scheme
where transmission occurs whenever the prediction error value Epred is
violated, the policy for the display unit 14 will most likely be set to always
listen for transmissions. However, the detection unit 14 could set a short
transmission window and only be able to broadcast during this time window
(as set in the policy). In this case, the detection unit 12 has the option of
whether to send data, set a new listening policy or do nothing at all during
each window. However, if the detection unit 12 detects a violation of the
compression error gcomp too often and is running out of inemory to store the
data or the prediction error epred is violated, the detection unit 12 has to
wait
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for the next transmission window to send data. In the worst case this could
result in erroneous data predicted by the display unit 14 and/or a loss of
data
by the detection unit 12. The detection unit 12 must also be careful not to
set
too long of a transmission period as memory overflow may occur in the
detection unit 12 and data will be lost. The display unit 14 could use the
policy
to identify potential interference between multiple detection units 12 (i.e.
two
or more detection units that want to broadcast at exactly the same time). It
would then be up to the display unit 14 to take the appropriate action to
resolve the conflict. Although in a unidirectional communication situation it
may be difficult to resolve the conflict without human intervention (in this
case,
the consumer would shut down the detection unit 12 and the display unit 14 to
reset these units). As shown in Table 1, the policy could be to broadcast
every
n Minutes, n Hours or n Days, where n is defined by the listen period field
128. If the listen policy field 126 is set to a time period of Minutes, Hours
or
Days then the 6 bits in the listen period field 128 allow for a listening
period
between 1 and 64 of the specified time period (i.e. 1 to 64 minutes, 1 to 64
hours or 1 to 64 days).
Table 1. Values for the Listen Policy Field
Code Polic
00 Alwa s
01 Minutes
10 Hours
11 Da s
[0072] The E_compression field 130 specifies the amount of
compression error Ecomp between true sensor readings and the compressed
values in the data that is transmitted. This value can range from 0 in the
lossless case to up to 255 for a very lossy compression scheme. The value in
the E_compression field 130 can be dynamically decided upon by the
compression unit 48 during compression.
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[0073] The E_prediction field 132 specifies the amount of prediction
error spred between the predicted values, due to the prediction model, and the
actual values before updated values for the model parameters are transmitted
by the detection unit 12 to the display unit 14. This value can range from 0,
which is the case where any violation of the prediction will result in a
transmission, up to 255. The value in the E-prediction field 132 can be
dynamically updated by the prediction unit 46. For example, if the power
source 30 is running very low, then this value may be increased so that fewer
transmissions are made by the detection unit 12. However, it is important that
the display unit 14 is aware of any possible error in the predicted values of
energy consumption so that the consumer can be properly notified via a
graphical output on the display 60.
[0074] The first and second history length fields 134 and 136 represent
the length of data in the compressed history data field 148. The first and
second history length fields 134 and 136 are specified by 12 bits in total to
represent data lengths from 0 to 4096 data points. The minimum length 0 is
specified when there is no data that is transmitted.
[0075] The compression type field 138 consists of 4 bits and specifies
the type of compression used for the data in the compressed history data field
140. For example, if the first bit in the compression type field 138 is a 1,
the
delta of the predicted series and the compressed series is compressed.
Alternatively, if the first bit of the compression type field 138 is a 0, then
the
raw sensor values are compressed. For different segments of a time series,
different compression schemes may work better. Accordingly, the
compression unit 48 can pick the best compression algorithm for a given
potion of data and represent the particular compression algorithm in the
compression type field 138. However, memory limitations in the detection unit
12 may not allow large blocks to have variable compression schemes. The
various compression schemes that can be used are represented in table 2
(currently two entries are reserved for using other different types of
compression). The entry NONE indicates that no compression is used.
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Table 2: T pes of data com ression
Code Compression
0000 NONE
0001 PMC-Raw
0010 Reserved
0011 PMC-Delta
0100 Reserved
[0076] The compressed history data field 140 is the compressed data
that is collected by the detection unit 12. The length of the data in the
compressed history data field 100 is specified in the history length fields
134
and 136 (to a max of 8192 bytes) and the type of compression used is
specified in the compression type field 138. As mentioned previously, the data
in the compressed history data field may be a series of values for the
prediction model parameters or may be the actual raw data. This is useful in
situations where the system 10 or 10' is configured for long times in between
data transmissions. For example, this may be once per day and the consumer
does not want real-time updated data but the consumer does want to see
what happened with power consumption at various times during the day.
[0077] The current value fields 142 and 144 represent the latest
absolute non-compressed current reading from the detection unit 12. This
value represents the cycle count up to (i.e. absolute cycle count) the latest
detected revolution of the power meter disk 18 prior to the current data
transmission. If a time index is necessary, then the time index should be
added to the data in the compressed history field 140.
Table 3. Meanin s for values in the Current Value Fields
Code Meanin
Ox0000...OxFFFE Sensor
Readin
OxFFFF No value
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[0078] The prediction model field 146 indicates the type of prediction
model used by the display unit 14 to predict the values between transmissions
from the detection unit 12. Exempfary representations in the prediction model
field 146 are shown in Table 4. The entry NONE indicates that no prediction is
used.
Table 4. Meanin s for values in the Prediction Model Field
Code Prediction
0000 NONE
0001 Last
0010 Linear
0011 Reserved
[0079] The model parameters field 148 provides the values for the
prediction model parameters that were generated by the prediction unit 46
according to the chosen prediction model. However, if the prediction model
field 148 specified that the prediction model is NONE, then all but the first
four
bits of this message will be encoded.
[0080] The transmission data structure 120 shown in Figure 4 gives no
indication of the error-correcting code (ECC) that is to be used during data
transmission. A strong ECC will have to be used in the case of unidirectional
communication if the detection unit 12 does not resend its information.
Otherwise the data sent by the detection unit 12 may not be recoverable.
Some examples of ECC include convolutional encoding and checking such as
VITERBI algorithms. The ECC works with an error detection code. In one
instance, CRC data can be added to the data transmitted and then used at
the receiver to provide error checking on the transmitted data. First the ECC
is
used to fix potential errors but if there are more errors than can be
corrected
the CRC is a fail safe mechanism to throw out the message.
[0081] Referring now to Figure 5, shown therein is a front view of an
embodiment of the display unit 160 that can be used with either of the power
meter reader systems 10 and 10'. The display unit 160 includes a display 162,
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a keypad 164, a communication port 166 and a power connection port 168.
The display 162 includes a number of display fields: a quantity display field
170, a unit display field 172, a power meter disk display field 174, a date
display field 176, a time display field 178 and a low battery indicator field
180.
The quantity display field 170 displays a numerical quantity such as the
quantity of power consumption or the temperature. The quantity display field
170 can display a$ symbol when displaying power consumption in a dollar
amount. The quantity display field 170 may also display icons that indicate
whether the quantity being displayed is for current energy consumption, total
energy consumption or future predicted energy consumption. The unit display
field 172 displays an appropriate unit for the quantity being displayed in the
quantity display field 170. The unit display field 172 can display the
following
units: C, F, Ibs CO2, kWh, etc. The power meter display field 174 displays a
digital representation of the power meter disk 18 including the black mark 20.
The digital representation of the power meter disk 18 rotates at the same
speed that the actual power meter disk 18 rotates. This field can also provide
a relative indication of the amount of energy consumption, such as a big
dollar
sign or a little dollar sign, to signify whether there is currently a large or
small
amount of energy that is being consumed. The date display field 176 displays
the current date and the time display field 178 displays the current time. The
low battery indicator field 180 can provide a display of a battery that is
almost
empty to indicate that the detection unit 12 is running out of power.
[0082] The keypad 164 includes an up-scroll key 182, a down-scroll
key 184 and a select key 186. The up-scroll and down-scroll keys 182 and
184 allow the user to scroll through different options such as scrolling
through
the type of numerical data that is to be displayed on the display 162, or
scrolling through the different locations so that the consumer may select the
location in which the power meter reader system is being used, etc. The
select key 184 is used to select one of the options.
[0083] The communication port 166 is used to connect the display unit
160 to a computer or another suitable computing device, as described in the
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description of the power meter reader system 10'. The power connection port
168 is used to connect the display unit 160 to a power source. Most likely, an
adaptor may be used to connect the display unit 160 to an electrical outlet.
[0084] Referring now to Figures 6a, and 6b, shown therein are views of
an exemplary physical embodiment of a detection unit 200 of the power meter
reader system attached to a power meter 202. The power meter 202 is a
conventional meter with a durable outer casing 204, a cover 206, a power
meter disk 208 and a plurality of dials 210. The cover 206 is made of glass or
piastic, has circular sidewalls with a flat front face and is transparent to
allow
an individual to read the dials 210 which indicate power consumption. The
power meter disk 208 is usually made from aluminum or another suitable
metal, and is flat with a black mark at a predetermined location along its
outer
edge. The power meter disk 208 rotates about a vertical axis at a rate that is
dependent upon the current drawn by the structure which is being monitored
by the power meter 202; the more current that is used, the faster the power
meter disk 208 rotates. The power meter 202 is sealed to provide protection
from the elements and to prevent tampering with the power meter disk 208
and the dials 210. The power meter 202 is of conventional construction the
inner workings are known by those skilled in the art. It should be noted that
the power meter 202 is shown for exemplary purposes and that the display
unit 200 can be mounted to other different power meter designs.
[0085] The detection unit 200 has been specially designed to fit and
work with different shapes and sizes of power meters. The detection unit 200
has also been specially designed so that it does not block the power meter
disk 208, the dials 210 or the serial number when it is attached to the power
meter 202 so that a person from the utility company can read the power meter
202 if needed. The detection unit 200 includes a main body 212, an extension
member 214 and an attachment means 216 for attaching the detection unit
200 to the power meter 202. The main body 212 houses most of the
electronics of the detection unit 200.
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[0086] The extension member 214 houses at least a portion of the
sensor unit 22 (i.e. the LED emitter and detector, and associated circuitry)
in a
head region 218. The extension member 214 also includes a longitudinal
extension means 220 and a pivot means 222 for positioning the sensor unit
22 over the power meter disk 208. In this embodiment, the longitudinal
extension means 220 comprises a slot 220a and a fastener 220b (in this case
a screw for example, although other suitable fasteners may be used). The
extension member 214 is extended over the face of the power meter 200, via
the longitudinal extension means 220, until the head region 218 of the power
meter 200 is directly over an appropriate region of the power meter disk 208.
In particular, the head region 218 is preferably located so that the sensor
unit
22 lies directly over the center of the power meter disk 208 because this is
the
location at which the black mark on the power meter disk 208 comes closest
to the front face of the power meter 202. Accordingly, this is the point at
which
the SNR of reflected signals will be highest for the sensor unit 22. The
fastener 220b is then placed through the slot 220a to engage a borehole 220c
(see Figure 6c) in the main body 212 to maintain the extension member 214
with a certain amount of extension and at a certain angle with respect to the
main body 212. In this embodiment, the fastener 220b and the borehole 220c
also provide the pivot means 222. The extension member 214 can be placed
at an angle other than 90 degrees (as is currently depicted in Figures 6a and
6b) with respect to the main body 212. It should be understood by those
skilled in the art that other implementations are possible for the
longitudinal
extension means 220 and the pivot means 222. For instance, the extension
member 214 can include a telescopic section for implementing the
longitudinal extension means 220.
[0087] The attachment means 216 is used to attach the detection unit
200 to the power meter 202. In this embodiment, the attachment means 216
includes a hose clamp 224 that slideably, releasably engages a loop member
226 on the main body 212 and extends around the perimeter of the power
meter 202 to secure the detection unit 200 to the power meter 202. The hose
clamp 224 is preferably made from a durable material that is either flexible
(or
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thin enough to be flexible) such as steel. The hose clamp 224 has a series of
serrations so that the clamping portion (not shown) can attach at a number of
positions to accommodate power meters 202 with a variety of different
diameters. However, in general, any appropriate clamping means can be
used for the attachment means such as clamps that include a lever, a latch
(such as an over-center latch), or a ratchet means for providing a tight fit
for
the attachment means.
[0088] Referring now to Figure 6c, shown therein is an exploded
isometric view of the main body 212 and the extension member 214 of the
detection unit 200 of Figure 6a. The main body 212 includes a first piece 212a
and a second piece 212b which are molded to provide a friction fit with one
another. The head region 218 includes a first piece 218a and a second piece
218b that are also molded to provide a friction fit with one another. The
electronics of the sensor unit 22 are housed between the first piece 218a and
the second piece 218b. The electronics of the remainder of the detection unit
200 are housed between the first piece 212a and the second piece 212b.
[0089] Referring now to Figure 7, shown therein is a power meter 320
showing four output locations 330A, 33013, 330C and 330D for indicating
power usage. The power meter 320 generally corresponds to the power
meter 220, except for having different output locations. These four output
locations are examples of the range of locations at which detection unit 340
(shown in Figures 8a to 12) is capable of reading. More specifically, Figures
8a to 8c show another alternative physical embodiment of a detection unit 340
in a projected configuration, capable of reading an output at location 330A.
Figure 9 shows detection unit 340 in a pivoted configuration, capable of
reading an output at location 330B. Figures 10a to 10c show detection unit
340 in a folded configuration, capable of reading an output at location 330C.
The detection unit 340 in the folded configuration shown in Figures 10a to 10c
can be easily arranged to read an output at location 330D.
[0090] The detection unit 340 is designed to fit and work with different
shapes and sizes of power meters. Typically, if the power meter is
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electromechanical and contains a power meter disk 332, the detection unit
340 will read the output in the projected configuration (as shown in Figures
8a
to 8c). The pivoted and folded in configurations of the detection unit 340 (as
shown in Figures 9, and 10a to 10c) are typically used for power meters with
outputs at difFerent locations, as described in further detail below.
[0091] As shown in Figures 8a to 8c, the detection unit 340 is designed
so that it does not block the power meter disk 332, the dials 334 or the
serial
number when it is attached to the power meter 320 so that a person from the
utility company can read the power meter 320 if needed.
[0092] The detection unit 340 includes a main body 346, an extension
member 342 and an attachment means 360 for attaching the detection unit
340 to the power meter 320. The main body 346 houses most of the
electronics of the detection unit 340 and is typically made of a suitable
plastic,
such as LEXANT"" for example, although other material may be used.
[0093] The extension member 342 houses the at least a portion of the
sensor unit 22 in a head region 344. The extension member 342 is extended
over the face of the power meter 320 until the head region 344 of the power
meter 320 is directly over an appropriate region of the power meter disk 332.
In particular, the head region 344 is typically located so that the sensor
unit 22
lies directly over the center of the power meter disk 332 because this is the
location at which the black mark on the power meter disk 332 comes closest
to the front face of the power meter 320. Accordingly, this is the point at
which
the signal to noise ratio of reflected signals are the highest for the sensor
unit
22.
[0094] Referring to Figures 11-13, the extension member 342 also
includes a longitudinal extension means for positioning the sensor unit 22
over the power meter disk 332. The extension means comprises an extension
support member 350, which maintains the extension member 342 with a
certain amount of extension with respect to the main body 346. Specifically,
when latch 352 is in the open position, it allows free movement of extension
member 342 in a channel or socket 354 provided by the extension support
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member 350. When the latch 352 is in the closed position (folded down) it
puts pressure on the extension means and holds it in place by friction. It
should be noted that the extension member 342 can be removably held in
place in other ways; for instance, the extension member 342 may make a
friction fit in the socket 354 provided by the extension support member 350.
Alternatively, the extension member 354 may include teeth, texturing or over-
molded rubber to help lock the extension member 354 in the desired position.
[0095] Referring now to Figure 9, shown therein is a front view of the
detection unit 340 of the power meter reader system attached to a power
meter 320 in a pivoted configuration. The combination of the extension
member 342 and the extension support member 350 provides a pivoting
means for positioning the sensor unit 22 over an output location such as
33013, as shown in Figure 7. More particularly, the pivoting means comprises
the extension support member 350, the socket 354 and the width of the
extension member 342 relative to the width of the socket 354. The socket 354
is larger than the width of the extension member 342 providing a free-play
distance equal to the difference in size, such that one may pivot the
extension
member 342 within socket 354 of the extension support member 350. As the
extension member 342 is extended further, the amount of pivot will increase,
and as the extension member is slid further into the socket the amount of
pivot will decrease. The relationship for pivot movement is roughly equal to
an
TAN"' relationship (i.e. free-play / arm-length inside socket). In a similar
fashion for adjusting the amount of extension for the extension member 342,
the latch 352 allows pivoting movement of the extension member 342 when
the latch 352 in the open position and secures the extension member 342
when the latch 352 is in the closed position.
[0096] It should be understood by those skilled in the art that other
implementations are possible for the extension means and the pivot means.
For instance, the extension means can include a telescopic element for
extending the length of the extension member 342. Further, the pivot means
may include a screw, and the extension member 342 may include a borehole
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that can be used to secure the position of the extension member 342 once it
has been pivoted into the desired location. Further, the free-play between the
width of the socket 354 and the width of the extension support member 350
can be increased, to support a larger degree of pivoting if needed. The socket
354 may also be designed such that the walls of the socket 354 have curves
or recesses, and the extension member 342 may be designed with thicker or
thinner sections such that the amount of pivoting is increased or decreased
for various extension lengths. In an alternative embodiment, the end of the
extension member 342 that is received by the socket 354 can have a ball-
shape and the socket 354 can have a similar sized rounded shape such that
the extension member 342 would only pivot when the ball of the extension
member 342 clicks into place in the socket 354 dictated by the amount of free-
play between the widths of the socket 354 and the extension support member
350.
[0097] Referring now to Figures 10a to 10c, shown therein are views of
the detection unit 340 in a folded configuration and attached to a power meter
320. As shown, the folded configuration is used to place the sensor unit 22
over an output location on the periphery of the cover 322 of the power meter
320 (such as locations 330C or 330D in Figure 7). In the folded configuration,
the extension member 342, including head region 344, is tucked against the
interior of the housing of the detection unit 340. In this particular
exemplary
configuration, a recess 348 (shown in Figure 11) in the interior of the main
body 346 of the detection unit 340 is provided to receive the extension
member 342 to provide a more compact fit when the detection unit 340 is
mounted to the power meter 320. Once in the folded configuration, the
detection unit 340 may then be slid onto or otherwise rotated around the
circular glass enclosure of the cover 322 so that the sensor unit 22 aligns
with
a particular output location.
[0098] Referring now to Figure 11, shown therein is a detailed view of
the inner surface of the detection unit 340. As shown, in the folded
configuration, the extension member 342 is removed from the socket 354 of
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the extension support member 350. To allow the detection unit 340 to be
configured in the folded configuration, the latch 352 is placed in its open
position so that the extension member 342 can be slid out of the socket 354 of
the extension support member 350. However, the extension member 342 is
still connected to the detection unit 340 by a cable 356 so that data can be
transmitted from the sensor unit housed in the head 344 region of the
extension member 342. The housing of the detection unit 340 can also
include a recess 348 for receiving the extension member 342. Various shapes
are possible for the recess 348 including a shape that is complementary to the
shape of the extension member 342 to provide a friction fit (see Figures 12a-
12d).
[0099] The attachment means 360 is used to attach the detection unit
340 to the power meter 320. In this exemplary embodiment, the attachment
means 360 includes a hose clamp 362 that slideably, releasably engages at
least one loop member 364 on the main body 346 and extends around the
perimeter of the power meter 320 to secure the detection unit 340 to the
power meter 320. The hose clamp 362 is preferably made from a durable
material that is either flexible (or thin enough to be flexible), such as
steel. The
clamping portion 360c (see Figure 13) of the hose clamp 362 can be used to
vary the diameter of the hose clamp 362 so that the detection unit 340 can be
attached to various power meters having a variety of different diameters. In
general, any appropriate clamping means can be used for the attachment
means such as clamps that include a lever, a latch (such as an over-center
latch), or a ratchet means for providing a tight fit for the attachment means.
A
clamp-like band made from a suitable type of nylon or rubber can also be
used for the attachment means 360. In alternative embodiments, other types
of attachment means may be used such as double-sided tape or other
suitable adhesives.
[00100] Referring to Figures 12a to 12d, shown therein are perspective
views of the detection unit 340 showing the steps for moving the position of
the extension member 342, which contains at least a portion of the sensor unit
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22, into the folded configuration. Figure 12a shows the detection unit 340 in
the projected configuration. From the projected configuration, the latch 352
is
opened and the extension member 342, including head region 344, is
removed from the socket 354 (see Figure 12b). For clarity, certain details of
the detection unit 340 are not shown, such as the cable 356 and the
attachment means 360. The extension member 342 is then flipped around
and placed in the extension member recess 348 of the main body 346 in such
a way that the sensor unit 22, located in head region 344, faces away from
the inner surface of the housing of the detection unit 340. Accordingly, once
the detection unit 340 is placed onto the power meter 320, the sensors in the
sensor unit 22 will face into the periphery of the cover 322 of the power
meter
340 (see Figures 12c and 12d). In an alternative, there may be sensors on
both sides of head region 344, which would eliminate the need to twist the
extension member 342, as shown in Figure 12b. Further, only the sensors on
the side of the head facing the power meter 320 are enabled. Figure 12d
shows the detection unit 340 in the folded configuration.
[00101] The recess 348 can have a substantially similar shape to
extension member 342 such that the recess 348 tightly secures the extension
member 342. Alternatively, the recess 348 can be shaped to allow for
movement of the extension member 342 so that the position of the sensor unit
22 can be adjusted to line up with the output location of the power meter 320.
For example, the recess 348 can have a region that has the same width as
the head region 344 of the extension member 342, to provide a friction fit but
have a longer length to allow the extension member 342 to be moved up or
down. Other variations are also possible. In each of these cases, the
extension member recess 348 can be made from conformal foam in which the
extension member 342 is placed in a friction fit. However, it should be
understood by those skilled in the art that the extension member 342 can be
secured in the recess 348 by any other suitable means. For example, rather
then have a suitably shaped recess, the detection unit 340 may include
somewhat flexible prongs or flanges that are spaced to slideably and
releasably receive a portion of the extension member 342 in a friction fit.
CA 02602867 2007-09-18
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[00102] Referring now to Figure 13, shown therein is an exploded view
of the housing of detection unit 340. The attachment means 360 attaches to
the main body 346 by engaging the loop members 364 (only one is shown).
The extension member 342 includes the head region 344, the sensor unit 22
(not shown), an aperture 344a for allowing the sensor unit 22 to emit or
receive a light signal, and a cradle 344c for holding at least a portion of
the
sensor unit 22, such as the LED emitter and detector, plus any associated
circuitry and wire connections that are required. The extension member 342
further includes the cable 356 with a connector 356c to connect the sensor
unit 342 to the remainder of the electronics of the detection unit 340 housed
within the main body 346.
[00103] The housing for the detection unit 340 also includes a PCB
cradle 370 to receive a printed circuit board 372 that includes the remainder
of
the electronics and slides into the main body 346. The printed circuit board
372 also includes baftery contacts 374 for receiving batteries.
[00104] The housing also includes a base plate 376 which makes a
friction fit on the first region 346a of the main body 346. The extension
support
member 350 makes a friction fit onto the base plate 376. The clamp 352 is
then pivotally connected to the extension support member 350. The
connection 356c is then connected to a corresponding connection on the PCB
cradle 370, and the extension member 342 is then slid into place in the
extension support member 350.
[00105] A housing lid 380 is placed beside the extension support
member 350 and attached to a second region 346b of the main body 346 with
a hinge pin 372 and a lid tab 384. The housing lid 370 enables access to the
main body 346 for example to facilitate the replacement of batteries (not
shown), which are housed inside main body 346. Accordingly, the housing lid
370 includes a battery contact strap 378, which connects the batteries
together to complete the circuit thereby providing energy to the detection
unit
340 when the housing lid 370 is closed. The lid tab 384 snaps into place on
the housing lid 370 such that the lid tab 384 can rotate. To lift the housing
lid
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370, the lid tab 374 can be rotated to the left so that a portion of the lid
tab
374 extends beyond the edge of the housing lid 370 so that a user can grab
this portion of the lid tab 374 and lift the housing lid 370.
[00106] In another embodiment, the detection unit 200 may contain an
additional sensor unit located along the inner surface of the housing. This
additional sensor unit can be used to read an output located on the periphery
of the cover 322 of the power meter 320.
[00107] It should be understood that while the detection units 200 and
340 are shown with both an extension means and a pivot means, in other
embodiments, these detection units can be designed to have either an
extension means or a pivot means.
[00108] It should be understood by those skilled in the art that while the
power meter 16 described herein is an electromechanical meter, the power
meter reader system described herein may also work with a digital power
meter unit. Digital power meter units provide an output that emulates the
rotation of the power meter disk. The output is usually on an LED or LCD
screen and could be a mark that rotates, or flashes or travels horizontally at
the same rate as the black mark on the power meter disk 18 would rotate. In
each of these cases, the sensor unit 22 can be used to sense the movement
of the mark. Accordingly, in general, the power meter reader described herein,
and more particularly the sensor unit 22, monitors a cyclical property of an
indication on a power meter reader that has a varying period that indicates
power consumption. The cyctical property could be the rotation of the black
mark on the power meter disk, the flashing of a mark on an LED screen, the
rotation of a mark on an LED screen or any other repetitive movement of the
mark on the LED screen. In these cases, the sensor unit 22 still operates in a
sleep mode when before and after the mark indicates the completion of one
cycle that is similar to one cycle or rotation of the power meter disk 18.
[00109] In addition, in another alternative, the digital power meter may
emit infrared energy that indicates the power consumption of the structure. In
this case, the sensor unit 22 does not emit infrared energy. Rather, the
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receiver of the sensor unit 22 operates using a sleep mode and tracking to
reduce power consumption, while detecting rotations of the simulated power
meter disk. The remainder of the power meter system works as previously
described. Further, the transmission protocol that is used to reduce power
consumption does not depend on whether the power meter unit is
electromechanical or digital.
[00110] It should also be understood that power meters 320 may have
other types of output such as ultra-violet, visible light, sound, ultra-sound,
magnetic energy, reflective or transfiective liquid crystal displays, or other
means of indicating power consumption with a cyclical property indicative of
the power consumption of the structure. The power meter reader described
herein can be modified to read these various types of outputs. Further, the
various housing structures described herein can be used to attach the power
meter reader to these different types of power meters.
[00111] In one aspect, at least one embodiment described herein
provides a detection unit that is mounted to the power meter unit and a
display unit that is remotely located with respect to the detection unit; one
possibility is to mount the display unit within the structure for which the
power
meter unit is monitoring energy consumption. The detection unit monitors the
indication of power consumption on the power meter (which is usually the
rotation of the power meter disk of the power meter) and provides information
related to the power consumption to the display unit. The display unit then
displays the power consumption information to a consumer who is responsible
for the power consumption of the structure. The display unit can provide a
variety of information such as power consumption in a kW/hr or in a dollar
amount (or another foreign currency) as well as the greenhouse gas that is
being emitted due to the power usage.
[00112] The detection unit provides one or more energy efficient
features for reducing its own energy consumption. For instance, the detection
unit can enter a sleep mode during certain time intervals while detecting the
power consumption indicated by the power meter unit. Alternatively, or in
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addition, the detection unit can generate a prediction model that represents
information related to the power consumption and transmit the prediction
model parameters, rather than raw data, to the display unit which uses the
prediction model parameters to show power consumption (this may be done
in real-time). This reduces the amount of data that is transmitted to the
display
unit. This also reduces the amount of transmissions that are sent to the
display unit since data need only be transmitted when the values of the
prediction model parameters change.
[00113] In another aspect, at least one embodiment described herein
provides a power meter reader system for automatically reading a power
meter unit mounted on a structure that is consuming power. The power meter
unit includes an indication with a cyclical property having a period that
varies
at a rate indicative of power consumption of the structure. The system
comprises a detection unit mounted on the power meter unit for monitoring
the power consumption. The detection unit comprises a sensor unit disposed
adjacent to the power meter unit for monitoring the cyclical property of the
indication and generating a consumption detection signal; a processing unit
connected to the sensor unit for receiving the consumption detection signal
and generating an information signal, the processing unit further generating a
sensor enable signal to enable the sensor unit for only a portion of the
cyclical
property of the indication, the portion coinciding with a time interval
indicating
the completion of one period of the cyclical property, the time interval being
shorter than the period of the cyclical property; and, a transmitter connected
to the processing unit for receiving the information signal and transmitting a
transmission signal. The power meter reader system further includes a display
unit located remotely with respect to the detection unit. The display unit
receives the transmission signal and displays the power consumption.
[00114] In another aspect, at least one embodiment described herein
provides a power meter reader system for automatically reading a power
meter unit mounted on a structure that is consuming power. The power meter
includes an indication with a cyclical property having a period that varies at
a
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rate indicative of power consumption of the structure. The system comprises a
detection unit mounted on the power meter unit for monitoring the power
consumption. The detection unit comprises a sensor unit disposed adjacent to
the power meter unit for monitoring the cyclical property of the indication
and
generating a consumption detection signal; a processing unit connected to the
sensor unit for receiving the consumption detection signal and generating an
information signal, the processing unit including a prediction unit for
generating values for prediction model parameters for predicting energy
consumption data derived from the consumption detection signal and
incorporating the values of the prediction model parameters into the
information signal; and, a transmitter connected to the processing unit for
receiving the information signal and transmitting a transmission signal. The
power meter reader system further includes a display unit located remotely
with respect to the detection unit. The display unit receives the transmission
signal and displays the power consumption of the structure based on the
prediction model parameters.
[00115] In a further aspect, at least one embodiment described herein
provides a detection unit for use with a power meter unit mounted on a
structure that is consuming power, the power meter unit including an
indication with a cyclical property that varies at a rate indicative of power
consumption of the structure. The detection unit is mounted on the power
meter unit for monitoring the power consumption and comprises a sensor unit
disposed adjacent to the power meter unit for monitoring the cyclical property
of the indication and generating a consumption detection signal; and, a
processing unit connected to the sensor unit for receiving the consumption
detection signal and generating an information signal, the processing unit
further generating a sensor enable signal to enable the sensor unit for only a
portion of the cyclical property of the indication, the portion coinciding
with a
time interval indicating the completion of one period of the cyclical
property,
the time interval being shorter than the period of the cyclical property.
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[00116] In yet another aspect, at least one embodiment described herein
provides a detection unit for use with a power meter unit mounted on a
structure that is consuming power, the power meter unit including an
indication with a cyclical property having a period that varies at a rate
indicative of power consumption of the structure. The detection unit is
mounted on the power meter unit for monitoring the power consumption and
comprises a sensor unit disposed adjacent to the power meter unit for
monitoring the cyclical property of the indication and generating a
consumption detection signal; and, a processing unit connected to the sensor
unit for receiving the consumption detection signal and generating an
information signal, the processing unit including a prediction unit for
generating values for prediction model parameters for predicting power
consumption data derived from the consumption detection signal and
incorporating the values of the prediction model parameters into the
information signal.
[00117] In another aspect, at least one embodiment described herein
provides a method for automatically reading a power meter unit mounted on a
structure that is consuming power, the power meter unit including an
indication with a cyclical property that varies at a rate indicative of power
consumption. The method comprises:
a) sensing values for the cyclical property of the indication using
a sensor unit and generating a consumption detection signal;
b) generating an information signal based on data from the
consumption detection signal; and,
c) generating a sensor enable signal to enable the sensor unit
for only a portion of the cyclical property of the indication, the portion
coinciding with a time interval indicating the completion of one period of the
cyclical property, the time interval being shorter than the period of the
cyclical
property.
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[00118] In a still further aspect, at least one embodiment described
herein provides a method for automatically reading a power meter unit
mounted on a structure that is consuming power, the power meter unit
including an indication with a cyclical property having a period that varies
at a
rate indicative of power consumption of the structure. The method comprises:
a) sensing values for the cyclical property of the indication using
a sensor unit and generating a consumption detection signal; and,
b) generating an information signal based on data from the
consumption detection signal by generating values for prediction model
parameters to predict power consumption data derived from the consumption
detection signal and including the values of the prediction model parameters
in the information signal.
[00119] In a still further aspect, at least one embodiment described
herein can include a processing unit including a control unit for directing
the
activity of the processing unit and a tracking unit connected to the control
unit
for tracking the cyclical property of the indication and for generating a
sleep
period during which the sensor enable signal disables the sensor unit.
[00120] In a still further aspect, at least one embodiment described
herein can include a sleep period having a percentage of the last value of the
cyclical property of the indication.
[00121] In a still further aspect, at least one embodiment described
herein can include a sleep period that is adjusted based on a history of
values
for the cyclical property of the indication.
[00122] In a still further aspect, at least one embodiment described
herein can include a processing unit further comprising a prediction unit for
generating values for prediction model parameters to predict power
consumption data derived from the consumption detection signal, and wherein
the values of the prediction model parameters are incorporated into the
information signal rather than raw data in the consumption detection signal.
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[00123] In a still further aspect, at least one embodiment described
herein can include a prediction unit that updates the values of the prediction
model parameters when data generated by the prediction model parameters
differs from the power consumption data derived from the consumption
detection signal by a value greater than a prediction error value.
[00124] In a still further aspect, at least one embodiment described
herein can include a transmitter that transmits the transmission signal to the
display unit every time new values for the prediction model parameters are
calculated.
[00125] In a still further aspect, at least one embodiment described
herein can include a processing unit that further comprises a compression unit
for compressing data in the information signal.
[00126] In a still further aspect, at least one embodiment described
herein can include a detection unit that further comprises a temperature unit
for monitoring outdoor temperature and providing a temperature signal to the
processing unit, and wherein data from the temperature signal is incorporated
into the information signal.
[00127] In a still further aspect, at least one embodiment described
herein can include a display unit that comprises: a display processing unit
for
controlling the operation of the display unit; a receiver connected to the
display processing unit for receiving and processing the transmission signal
to
provide a received signal to the display processing unit; a display connected
to the display processing unit for displaying information related to power
consumption of the structure; and, an interface unit connected to the display
processing unit for allowing a user to input information and select modes of
operation for the display unit.
[00128] In a still further aspect, at least one embodiment described
herein can include a display unit that further comprises: a real-time clock
connected to the display processing unit for providing time information; a
buzzer unit connected to the display processing unit for providing audible
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information to the user; and, a memory unit connected to the display
processing unit for storing information related to power consumption of the
structure.
[00129] In a still further aspect, at least one embodiment described
herein can include a display unit that further comprises a communication unit
connected to the display processing unit for providing a connection to an
external computing device for uploading the power consumption information
and downloading power consumption rates.
[00130] In a still further aspect, at least one embodiment described
herein can include a display unit that comprises: a display processing unit
for
controlling the operation of the display unit; a receiver connected to the
display processing unit for receiving and processing the transmission signal
to
provide a received signal to the display processing unit, and, an appliance
control unit connected to the display processing unit for controlling at least
one appliance in the structure, the appliance control unit receiving at least
one
of temperature information, power consumption information and time
information and generating an appliance control signal for controlling an
operational setting of the at least one appliance.
[00131] In a still further aspect, at least one embodiment described
herein can include a sensor unit that comprises an emitter, a first detector
and
a second detector, each directed towards a location where the indication
appears, the emitter being disposed between the first and second detectors,
the emitter being adapted to emit IR energy at the location where the
indication appears, and the first and second detectors are adapted to detect a
level of IR energy related to the indication, the first and second detectors
providing first and second detection signals indicative of the period of the
cyclical property of the indication.
[00132] In a still further aspect, at least one embodiment described
herein can include first and second detection signals that are combined using
the logical AND operator to provide the consumption detection signal.
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[00133] In a still further aspect, at least one embodiment described
herein can include first and second detection signals that are combined by
subtracting the first and second detection signals from one another.
[00134] In a still further aspect, at least one embodiment described
herein can include a display unit located remotely with respect to the
detection
unit, the display unit receiving the transmission signal and displaying the
power consumption of the structure based on the prediction model
parameters.
[00135] In a still further aspect, at least one embodiment described
herein can include a processing unit that includes a control unit for
directing
the activity of the processing unit and a tracking unit connected to the
control
unit for tracking the cyclical property of the indication and for generating a
sleep period during which the sensor unit is disabled, wherein the processing
unit provides an enabling value in a sensor enable signal to enable the sensor
unit for only a portion of the cyclical property of the indication, the
portion
coinciding with a time interval indicating the completion of one period of the
cyclical property, the time interval being shorter than the period of the
cyclical
property, otherwise the sensor enable signal being adapted to disable the
sensor unit based on the sleep period.
[00136] In a still further aspect, at least one embodiment described
herein can include a method that further comprises transmitting a
transmission signal based on the information signal; and at a remote location
relative to the power meter unit, receiving and processing the transmission
signal for obtaining power consumption information and, displaying the power
consumption information.
[00137] In a still further aspect, at least one embodiment described
herein can include a method that includes tracking the cyclical property of
the
indication for generating a sleep period during which the sensor enable signal
disables the sensor unit.
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[00138] In a still further aspect, at least one embodiment described
herein can include a method that further comprises generating the sleep
period as a percentage of the last value of the cyclical property of the
indication.
[00139] In a still further aspect, at least one embodiment described
herein can include a method that further comprises generating the sleep
period based on a history of values for the cyclical property of the
indication.
[00140] In a still further aspect, at least one embodiment described
herein can include a method that further comprises generating values for
prediction model parameters to predict power consumption data derived from
the consumption detection signal.
[00141] In a still further aspect, at least one embodiment described
herein can include a method that further includes updating the values for the
prediction model parameters when data generated by the prediction model
parameters difFers from the power consumption data derived from the
consumption detection signal by a value greater than a prediction error value.
[00142] In a still further aspect, at least one embodiment described
herein can include a method that further includes compressing data in the
information signal to produce the transmission signal.
[00143] In a still further aspect, at least one embodiment described
herein can include a method that further includes monitoring outdoor
temperature and incorporating temperature data into the information signal.
[00144] In a still further aspect, at least one embodiment described
herein can include a method that can further include storing information
related to the power consumption of the structure and, predicting future power
consumption of the structure based on the stored information.
[00145] In a still further aspect, at least one embodiment described
herein can include a method that further includes providing a connection to an
external computing device for uploading the power consumption information
and downloading power consumption rates.
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[00146] In a still further aspect, at least one embodiment described
herein can include a method that further comprises generating an appliance
control signal for controlling an operational setting of at least one
appliance in
the structure, the appliance control signal being generated based on at least
one of temperature information, power consumption information and time
information.
[00147] In a still further aspect, at least one embodiment described
herein can include a method that further includes transmitting the
transmission signal every time new values for the prediction model
parameters are calculated.
[00148] In a still further aspect, at least one embodiment described
herein can include a method that further includes: tracking the cyclical
property of the indication for generating a sieep period during which a sensor
enable signal disables the sensor unit; and, generating the sleep period
during which the sensor unit is disabled by providing an enabling value in the
sensor enable signal to enable the sensor unit for only a portion of the
cyclical
property of the indication, the portion coinciding with a time interval
indicating
the completion of one period of the cyclical property, the time interval being
shorter than the period of the cyclical property, otherwise the sensor enable
signal being adapted to disable the sensor unit based on the sleep period.
[00149] Finally, it should be understood that various modifications can
be made to the embodiments described and illustrated herein, without
departing from the scope of these embodiments which are defined in the
appended claims. For instance, the display unit need not be installed in the
structure that is consuming power since there are some applications in which
one display unit can be linked to several detection units so that power
consumption of several structures can be monitored from a central location. In
this case, the display unit needs to be augmented to recognize the identity of
several detection units and keep separate records for each detection unit.
