Note: Descriptions are shown in the official language in which they were submitted.
CA 02301700 2009-05-07
11ME442
ELECTRONIC ELECTRICITY METER
BACKGROUND OF THE INVENTION
This invention relates generally to electricity metering and more
particularly,
to an electronic electricity meter configurable to transmit information to a
central
computer via a modem unit.
In many electronic electricity meters, communications with a meter
microcomputer can be performed via an optical port or an option board
connector.
For example, in some known meters, an electrical connector is provided so that
various option boards, such as a telephone modem communication board, may be
electrically connected to the meter microcomputer. A central computer is often
used
to collect data, including billing information, from the meter, using the
modem
communication board. The data is available from the modem communication board
in a predefined format (an ANSI defined protocol) on the communication channel
which connects the option board connector to the meter microcomputer.
To reduce the number of nuisance and common event, e.g., power outage,
calls, it is desirable to provide a modem unit, or board, which detects
conditions
within the meter and exchanges information with the central computer after the
condition has existed for a pre-defined period of time. It also would be
desirable to
provide such a unit that would allow modification of the operation parameters.
It
would further be desirable to provide such a modem unit which can be easily
and
quickly coupled to a meter while allowing programming of a security password.
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BRIEF SUMMARY OF THE INVENTION
In an exemplary embodiment, an electricity meter includes a modem circuit,
or unit, coupled to the meter microcomputer which exchanges information
between
the meter microcomputer and a central computer of the data source. Using the
signals supplied by the meter microcomputer and the central computer, the
modem
unit can detect various conditions within the meter and determine the proper
time
for exchanging the information. In one embodiment, the modem unit includes a
microcomputer having a plurality of timers.
= In one aspect, the present invention is directed to allowing the
programming
of meter and modem unit passwords. Specifically, the meter and modem unit are
placed into a password recovery state upon detecting closure of an external
switch.
Closure of the external switch simultaneously places the meter and the modem
unit
into password recovery states so that new passwords may be programmed into the
meter and the modem unit by the central computer. Such a configuration avoids
the
time and expense associated with reprogramming the modem unit at the meter
shop
or having to send a specially trained individual to the meter site to perform
the
reprogramming.
In another aspect, the present invention is directed to limiting the number of
calls initiated from the meter. More specifically, the modem unit
microcomputer
detects certain events and waits a pre-defined period of time before
initiating the call
to the central computer. In one form, after the modem unit detects a power
outage
indicator from the meter microcomputer, the modem unit waits a programmable
period of time prior to an outage call being placed to the central computer.
The
modem unit microcomputer may be further configured so that in order to
initiate the
call to the central computer several conditions must occur within a pre-defmed
period of time. If all of the events do not occur in the specified period of
time, the
call will not be made to the central computer.
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In yet another aspect, the present invention is directed to the modem unit
answering calls from the central computer. More specifically, and in
accordance
with one form, the meter modem unit receives new program information from the
central computer. The modem unit microcomputer program is stored in a non-
volatile memory having two segments. A new program is stored in an inactive
segment of the memory while the modem unit microcomputer executes a program
from the active segment. If the programming is completed, the microcomputer
changes the inactive segment to the active segment and executes the new
program.
However, if the programming is not completed, the modem unit microcomputer
will
io continue to execute the program stored in the active segment. The two
segments
ensure that the meter will not be left in a partially programmed mode.
In still another aspect, the present invention is directed to utilizing
multiple
meters configured in a master slave arrangement. Information is exchanged
between the meters and the central computer utilizing a single telephone line.
More
specifically, each meter includes a modem unit having a unique identification
number. Prior to exchanging information from the central computer, an
identification number is transferred to the meters. Each modem microcomputer
determines whether the transferred identification number matches the
identification
number stored in its memory. If the numbers match, that modem unit exchanges
information with the central computer. Those meters which do not match the
transferred identification number wait and listen for the next transferred
identification number to determine whether a match exists.
The above described modem unit detects multiple conditions and responds to
those conditions at the proper pre-defined time to reduce the number of
nuisance and
common event calls. New operation parameters may also be transferred to the
modem unit to allow modification of the condition and time parameters. The
modem unit described above allows the password to be reprogrammed and the user
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does not have to pre-program the modem unit. As result, a new modem unit may
be
quickly installed in a meter.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a block diagram of an electronic energy meter.
Figure 2 is a block diagram of a modem unit in accordance with one
embodiment of the present invention.
Figure 3 is a flow chart of operation of the meter in accordance with one
embodiment of the present invention.
Figure 4 is a flow chart illustrating a sequence of process steps for
detecting
a condition in an electronic electricity meter.
Figure 5 is a flow chart illustrating a sequence of process steps for
detecting
a password recovery state in an electronic electricity meter.
Figure 6 is a flow chart illustrating a sequence of process steps for
detecting
a power outage state in an electronic electricity meter.
Figure 7 is a flow chart illustrating a sequence of process steps for placing
an
outage call in an electronic electricity meter.
Figure 8 is a flow chart illustrating a sequence of process steps for
generating a status report in an electronic electricity meter.
Figure 9 is a flow chart illustrating a sequence of process steps for call
answer state in an electronic electricity meter.
Figure 10 is a block diagram of a master/slave configuration in accordance
with one embodiment of the present invention.
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Figure 11 is a flow chart illustrating a sequence of process steps for a
master/slave configuration of an electronic electricity meter.
DETAILED DESCRIPTION OF THE DRAWINGS
Figure 1 is a block diagram illustration of an exemplary electronic energy
meter 10 which, for example, is commercially available from General Electric
Company, 130 Main Street, Somersworth, N.H. 03878, and generally referred to
as
the KV meter. The KV meter can be modified to incorporate the modem unit
described below in more detail. Although the present apparatus and methods are
described herein in the context of an electronic electricity meter, it should
be
understood that the present invention is not limited to practice with any one
particular meter. The present invention can be utilized in connection with
other
microcomputer based meters.
Referring now specifically to Figure 1, meter 10 includes voltage sensors 12
and current sensors 14. Sensors 12 and 14, in operation, typically are coupled
to
the power lines supplying power to site at which the meter is located. Sensors
12
and 14 are coupled to an analog to digital (A/D) converter 16 which converts
the
input analog voltage and current signal to digital signals. The output of
converter
16 is provided to a digital signal processor (DSP) 18. DSP 18 supplies
microcomputer 20 with digitized metering quantities, e.g., V2H, I2H.
Microcomputer 20, using the metering quantities supplied by DSP 18, performs
additional metering calculations and functions. DSP 18 may, for example, be a
processor commercially available as Model Number TMS320 from Texas
Instruments Company, P.O. Box 6102, Mail Station 3244, Temple, TX 76503,
modified to perform metering functions.
Microcomputer 20 is coupled to a liquid crystal display 22 to control the
display of various selected metering quantities and to an optical
communications
port 24 to enable an external reader to communicate with computer 20. Port 24
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may be the well known OPTOCOMTm port of General Electric Company, 130 Main
Street, Somersworth, N.H. 03878, which is in accordance with the ANSI type IL
optical port. Microcomputer 20 may also generate additional outputs 26 used
for
various other functions as is well known in the art. Microcomputer 20 may, for
example, be an eight bit microcomputer commercially available from Hitachi
America, Inc., Semiconductor & I.C. Division, Hitachi Plaza, 2000 Sierra Point
Parkway, Brisbane, CA 94005-1819, modified to perform metering functions.
Microcomputer 20, in one embodiment, also is coupled to an input/output
(I/O) board 28 and to a function, or high function, board 30. DSP 18 also
supplies
outputs directly to high function board 30. Microcomputer 20 further is
coupled,
via a control bus 32, to an electronically erasable programmable read only
memory
(EEPROM) 34. I/O board 28 and high function board 30 also are coupled, via bus
32, to FEPROM 34.
Back-up power is supplied to the meter 10 by a power outage battery 36
coupled to a wide range power supply 38. In normal operation when no back-up
power is required, power is supplied to the meter components from the power
lines
via power supply 38.
Many functions and modifications of the components described above are
well understood in the metering art. The present application is not directed
to such
understood and known functions and modifications. Rather, the present
application
is directed to the methods and structures described below in more detail. In
addition, although the methods and structures are described below in the
hardware
environment shown in connection with Figure 1, it should be understood that
such
methods and structures are not limited to practice in such environment. The
subject
methods and structures could be practiced in many other environments.
Further, it should be understood that the present invention can be practiced
with many alternative microcomputers, and is not limited to practice in
connection
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with just microcomputer 20. Therefore, and as used herein, the term
microcomputer is not limited to mean just those integrated circuits referred
to in the
art as microcomputers, but broadly refers to microcomputers, processors,
microcontrollers, application specific integrated circuits, and other
programmable
circuits.
Figure 2 is a block diagram of an exemplary modem circuit, or unit, 50 in
accordance with one embodiment of the present invention. Generally, unit 50
couples to meter microcomputer 20 as described below in more detail and at
least
based in part on the signals present at unit 50, unit 50 can determine whether
meter
10 should take any action as described below.
Referring now specifically to Figure 2, unit 50 includes a microcomputer 52
coupled to meter microcomputer 20, a memory 54, and a modem circuit 56. Unit
50 provides a communication path, or link, for exchanging data, or
information,
between meter 10 and a central computer 58. Microcomputer 52 includes, in one
embodiment, a random access memory (RAM) 60 and a read only memory (ROM)
62. Programmed parameters and operating information, or data (not shown), are
stored in memory 54. Memory 54 may, for example, be a non-volatile memory
device such as an electrically erasable read only memory (FFPROM), although
other types of non-volatile memory devices may be used. Modem circuit 56 may,
for example, be a modem chipset commercially available as Model Number
RC224AT from Rockwell International Corp., Digital Communications Division,
4311 Jamboree Road, Newport Beach, CA 92660.
Command, response, and communication data are exchanged between
microcomputer 52 and modem circuit 56. A telephone interface circuit 64
couples
modem circuit 56 to a telephone line 66 so that information may be remotely
exchanged between meter 10 and central computer 58. In one embodiment, modem
unit microcomputer includes a timer circuit 80 having a plurality of timer
circuits
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for measuring time. Timer circuit 80 includes a real-time clock 82, an outage
timer
84, an outage delay timer 86, and a call delay timer 88. Real-time clock 82
generates a time value representative of the current time and date, e.g.,
HII:MM:SS, MM/DD/YY. Timers 84, 86, and 88 are used for measuring the
amount of time that has passed since a certain event, or occurrence of a
condition.
Timers 84, 86, and 88 may be programmed with an initial value and may
increment
or decrement in value and produce a signal when the programmed time has passed
or elapsed. In an alternative embodiment, timer circuit 80 may be separate and
distinct from modem unit microcomputer 52.
To exchange information between meter 10 and central computer 58, and in
one embodiment, a data exchange algorithm is loaded into modem unit 50.
Specifically, the algorithm is loaded, and stored, in memory 62. The algorithm
is
then executed by microcomputer 52.
A flow chart 100 illustrating process steps executed by microcomputer 52 in
exchanging information between meter 10 and central computer 58 is set forth
in
Figure 3. More particularly, upon power up 102 of meter 10, or anytime after
power is applied to meter 10, various parameters are programmed 104 into
memory
54. In
one embodiment, the parameters include initial values for tinier circuits 80,
specifically, initialintion of timers 84, 86, and 88, whether an outage call
should be
placed, how long should meter 10 wait before placing call, and whether meter
10
should answer a call from the central computer 58. In addition, after the
parameters
are programmed and power is applied to meter 10, outage delay timer 86 is
started.
After programming parameters 104, microcomputer 52 monitors operations
of meter 10 to determine, or detect, whether a condition exists, or a change
has
occurred 106 in the signals provided to modem unit 50. The conditions include
an
error, a caution, and a diagnostic condition. If a condition is detected 106,
information is transferred, or exchanged, 108 using modem unit 50.
Particularly,
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microcomputer 52 detects modifications of signals provided from meter
microcomputer 20 to modem microcomputer 52 and in the signals provided from
central computer 58. More specifically as shown in Figure 4, microcomputer 52
detects 106 at least the following the conditions or changes and exchanges 108
the
indicated information.
Detect Condition 106 Information Exchange 108
1. Password Recovery 110 Recover password 114.
2. Power outage 118 Power outage call 122.
3. Scheduled Status Report 126 Status Call 130
4. Call from central computer 134 Answer Call 138.
5. New Program 142 Update Program 146.
6. Master/Slave mode 150 Master/Slave Update 154
Password Recovery and Recover Password
Password recovery 110 and recover password 112 refer to detecting a
password recovery state and enabling programming of modem unit 50 password and
meter 10 password. In one embodiment, an external switch, oerable by a user,
generates a PW_Recovery signal that is supplied to modem unit 50 from meter
microcomputer 20. The PW_Recovery signal is supplied to microcomputer 52 in a
low to high state to enable the programming of the passwords. More
particularly,
and referring to Figure 5, recovering password 114 includes disabling the
password
security 200 of modem unit 50 and placing modem unit 50 in a password recovery
state 202. Disabling security 200 allows microcomputer 52 of modem unit 50 to
continue to operate without having a password that matches the meter password.
After modem unit 50 is placed in the recovery state 202, the same password is
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stored 204 in meter 10 and modem unit 50. Specifically, the passwords
transmitted
from central computer 58 to meter 10 utilizing modem unit 50. The passwords
are
then programmed in meter microcomputer 20 and modem unit memory 54. Upon
completion of programming the new passwords into microcomputer 20 and memory
54, the PW_Recovery signal supplied to microcomputer 52 is changed to a false,
or
low state by meter microcomputer 20. Password security of modem unit 50 is
enabled 208 after modem unit 50 receives the new passwords.
For example, if a new modem unit 50 is installed and coupled to a
microcomputer 20, the meter password and the modem unit password would not
match, therefore, meter 10 may not be able to be programmed to extend the
functionality of meter 10. As a result of recover password 114, modem unit 50
and
microcomputer 20 will have matching passwords.
Power outage and power outage call
Power outage 118 and power outage call 122 refers to notifying central
computer 58 when the power is removed from meter 10. A power outage signal is
supplied to modem unit 50 from meter microcomputer 20 to indicate that power
has
been removed from meter 10. Specifically, the power outage signal supplied by
microcomputer 20 changes from a false state, to a true state when power is
removed
from meter 10. More specifically and as shown in Figure 6, upon microcomputer
52 detecting power outage 118, power is supplied 220 to microcomputer 52 from
outage battery 36. Microcomputer 52 updates 222 a meter status signal which is
stored in memory 54. Outage timer 84 is then started 224 and the outage delay
timer is stopped and the value stored 226 in memory 54. The value of outage
timer
84 is then monitored 228 using microcomputer 54 to determine whether the value
of
outage timer 84 is within a valid range. If power is not restored to meter 10
prior to
the value of outage timer 84 being within the valid range, microcomputer 52
examines 230 previous outage call completed parameter stored in memory 54 to
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determine whether an outage call should be placed. If the previous outage call
completed parameter stored in memory 54 is in a false state, a call is placed
232 to
central computer 58 as described below. If, however, the previous outage call
completed parameter is in a true state, microcomputer 52 examines 234 the
value of
outage delay timer 86 stored in memory 54 to determine whether the value is
within
a predefined, or valid range. If the value is within the predefmed range, a
call is
placed to central computer 58. If, however, the value is outside the valid
range,
microcomputer 52 resets 238 outage delay timer 86 and waits for power to be
applied to meter 10.
Outage timer 84 and outage delay timer 86 may be configured to avoid
nuisance outages calls caused by power transients and to alter the timing of
outage
calls from different meters in a common outage area. Specifically, outage
timer 84
may be configured to prevent calls from being made to central computer 58
until a
specific amount of time has passed. In one embodiment, outage timer 84 is
programmed with a value between 0, indicating no delay, and 255 seconds. If
the
value is programmed with a non-zero value, power must be removed from meter 10
at least for that period, or valid range, of time, before microcomputer 52
proceeds.
For example, in one embodiment, diagnostic tests, or checks, are delayed a
selectable period of time to allow stabilization of supplying power and meter
10. In
another embodiment, calls to central compute 58 are prevented until the
selected
period of time for stabilization has passed.
The value of outage timer 84 is altered to prevent nuisance calls from being
generated from power outages having a duration less than the programmed value
of
timer 84. In addition, outage delay timer 86 may be configured to prevent
nuisance
calls from transient conditions. For example, typical outages may consist of a
series
of power transitions before power is completely lost and short outages may
occur
during normal operation due to wind blown power lines or other relatively
brief
disturbances. Additionally, the process of repairing local power distribution
faults
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often produces several brief power restorations, followed by a loss of power,
before
power is restored permanently. In order to avoid multiple calls from being
made
from a plurality of meters, outage timer 84 and outage delay timer 86 may be
configured to require that power be removed for a pre-defined period of time
and
meter 10 to have power applied for a valid range of time before an outage call
is
made. Specifically, if the values of both timers 84 and 86 are not within
their
respective valid ranges a call will not be placed to central computer 56.
Referring to Figure 7, in placing a call 236 to central computer 58,
microcomputer 52 initializes 250 modem circuit 56. Initialization 250 includes
configuring circuit 56 to originate a call to central computer 58, defines a
phone
number to call for central computer 58, and defining parameters related to the
baud
rate, type of handshaking and other communication parameters as known in the
art.
If the outage call parameter is in a true state indicating that a call is to
be made
during a power outage condition, microcomputer 52 delays 252 a defined period
of
time for outage battery 36 to reach full charge. Call delay timer 88 is
started 254
and microcomputer 52 monitors 256 call delay timer 88 until the value of call
timer
equals the value, or valid range, defined during programming of parameters
104.
When the value of call delay timer is within the valid range, a status report
is
generated 258 by microcomputer 52 and a call is placed 260 to central computer
58
utilizing modem circuit 56. After the status report is generated 258, modem
circuit
56 supplies the status report to telephone interface 64 and telephone line 66
so that
the status report is transferred to central compute 58. If a call is completed
262,
modem circuit 56 supplies 264 an outage call completed signal to microcomputer
52
and power is removed 266 from modem circuit 56.
If the call is not completed, call delay timer 88 is reset and started 268.
Upon microcomputer 52 detecting 270 call delay timer 88 being within a valid
range, a second call is placed 272 to central computer 58. The second call may
be
placed to the same phone number as described above, or may be placed to a
second
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phone number for central computer 58. As described above, if microcomputer 52
detects 274 that the second call was completed, modem circuit 56 supplies 262
the
outage call completed signal to microcomputer 52 and power is removed 264 from
modem circuit 56. If the call is not completed, modem unit 50 is stopped and
waits
for power to be applied to meter 10. Additional configurations may also be
included, e.g., meter 10 may attempt any number of calls and any number of
different numbers prior to stopping.
In one embodiment and as shown in Figure 8, the status report generated 258
includes transferring status information, or data, from two tables stored in
memory
54. Specifically, microcomputer 20 periodically executes a diagnostic, or test
routine to update 300 status of meter 10. The results of the diagnostic
routine is
transferred from microcomputer 20 to microcomputer 52 and stored 302 in a
meter
status table in memory 54. A modem unit status routine is executed by
microcomputer 52 to update 304 status of modem unit 50. The resulting modem
unit status is stored in a modem status table in memory 54. The status report
generated 258 for transfer to central computer 58, includes the contents of
the meter
status table and the modem unit status table.
In another aspect of the present invention, in order to reduce the power
consumption of outage battery 36, outage battery 36 powers only modem unit 50
during a power outage. Specifically, in the event of a power outage, before
placing
260 call to central computer 58, microcomputer 52 updates the modem status
table
and stores the updated status in memory. Then, unneeded circuitry is placed in
a
low power sleep mode, until the outage call is placed. Once modem unit 50 is
connected to central computer 58, the status report, including all required
status
information is exchanged with to central computer 58 by transferring the meter
status table and the modem status table. As a result, the time required to
transmit
the information is reduced which reduces power consumption of outage battery
36.
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In another aspect of the present invention and in one embodiment, a statistics
communication algorithm is loaded in central computer 58. Specifically, the
algorithm is loaded, and stored, in a memory of central computer (not shown).
The
algorithm is then executed by a microcomputer, or microprocessor (not shown)
in
central computer 58. The central computer microcomputer records statistical
data
related to the information exchanged between meter 10 and central computer 58.
The statistical data includes status information and error information. Status
information is data concerning general byte counts and data packet counts.
Error
information is data specifically relating the number of errors, the number of
bytes
associated with an error, and the number of data packets associated with the
errors.
At the end of exchanging information between meter 10 and central computer 58,
central computer microcomputer analyzes the statistical data. If certain
portions of
the data meet a previously established error criteria, then the data is stored
in central
computer 58. The algorithm allows only data of interest to be stored thereby
saving
storage space and analysis time.
In another aspect of the invention, in order to prevent all meters in an
outage
area from calling central computer 58 at the same time, the valid range of
call delay
timer 88 may be unique to each meter 10. In one embodiment, a random delay is
generated for each meter 10. The random delay is based on the generation of a
random number in a specific range from an encrypted serial number seed, or
initial
value. For example, in one embodiment, the valid range of call delay tinier 84
is
based on the unique serial number of meter 10. Using the meter serial number,
microcomputer 52 generates a valid range for outage timer 84. Specifically,
microcomputer 52 utilizes the encrypted serial number to generate the valid
range
for outage timer 84. The nature of the encryption is such that two encrypted
serial
numbers generated from two consecutive meter serial numbers will generate very
different valid ranges for outage timer 84. As a result, meters in the outage
area
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generate outage calls at different times. The valid range of each meter 10 may
be
programmed to include any valid range.
Scheduled Call Detect and Scheduled Call
Scheduled call detect 126 and scheduled call 130 refer to detecting whether
the current time, as defined by real-time clock 82, is within a programmed, or
pre-
defined valid range. If the value of real-time clock 82 is within the valid
range, the
status report, as described above, is transferred to central computer 58.
Specifically, to transfer the status report, including billing information, to
central
computer 58, real-time clock 82 is monitored to determine whether the current
time
matches a value stored in memory 54. The scheduled call time value may be
defined to specify a certain time, day, day of the week, day of the month, or
a
combination thereof. Upon detecting 126 real-time clock 88 being within the
valid
range, modem unit 50 initiates a call to central computer 58 as described
above.
The status report, including the billing information, is then transferred to
central
computer 58.
Call from Central Computer and Answer Call
Call from central computer 130 and Answer Call 138 refer to central
computer 58 originating a call to meter 10. Specifically, and as shown in
Figure 9,
central computer 58 initiates a call to meter 10 utilizing telephone line 66.
Upon
detecting call, telephone interface supplies an incoming call signal to
microcomputer
52. If a call answer parameter is detected 300 in a true, or high state,
microcomputer 52 supplies a call answer signal to telephone interface 64 and
modem circuit 56 so that the call is answered 302. After answering the call
from
central computer 58, modem circuit 56 performs handshaking 304 with central
computer 58 so that data may be exchanged 306 between central computer 58 and
meter 10. Data continues to be exchanged 306 until the completion 308 of the
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exchange at which time modem circuit 56 and central computer 58 each hang up
310
and the call is terminated.
New Program and Update Program
New program 142 and update program 146 refer to transmitting a new
program to meter 10 from central computer 58. The new program is transmitted
from central computer 58 to meter 10 so that the new program is stored in
modem
unit 50. More specifically, the new program is transferred from central
computer
58 to modem unit 50 to alter operation of meter 10. For example, the new
program
may alter the time of the next scheduled call, the valid ranges for timer
circuits 80
and the call answer parameters, The new program may also provide new phone
numbers for calling central computer 58.
In one embodiment, the new program is stored in memory 54 including two
segments. Prior to receiving the new program from central computer 58, the two
segments are defined as an active segment containing the most recently
programmed
data, or program and an inactive segment containing previously programmed
data.
When a new program is received, the new program data is stored in the inactive
segment. If the programming session is successfully completed, a programming
complete signal is changed from the initialized low, or false state to a true,
or high
state. If the programming complete signal is detected to be in a high state
the
current active segment is changed to the inactive segment and the current
inactive
segment is changed to the active segment.
If the programming is not completed and the programming complete signal
does not transition to a high state, a loss of program call may be initiated
to central
computer so that the programming can be completed. When central computer 58
places call to meter 10, the original active and inactive segments
designations will
be unchanged because the new program was not successfully completed. As a
result
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the modem unit 50 will always have a valid program, including operating
parameters, so that unit 50 can continue to function properly.
Master/Slave Call and Master/Slave Update
Master/Slave Call 158 and Master/Slave Update 162 refer to placing a call to
a group of at least two meters coupled to central computer 58 utilizing a
single
phone line 66. Specifically and as shown in Figure 10, meters 500A, 500B,
500C,
500D, and 500 E are coupled to central computer 58 utilizing a single
telephone line
66. One meter, for example meter 500A, is designated as a master meter, while
the
remaining meters, 500B, 500C, 500D, and 500E are designated as slave meters.
Each meter includes a unique identification number, for example stored in
memory
54. Information, or data, is exchanged between central computer 58 and meters
500A, 500B, 500C, 500D, and 500E utilizing telephone line66.
Referring to Figure 11, when a phone call from central computer 58 is
directed to meters 500A, 500B, 500C, 500D, and 500E utilizing phone line 66,
meters 500A, 500B, 500C, 500D, and 500E answer 602 call. Specifically,
after master meter 500A handshakes 604 with central computer 58, meters 500A,
500B, 500C, 500D, and 500E each monitor 606 an incoming message, or data
packet transferred from central computer 58. The incoming message includes an
identification number that corresponds to one of meters 500A, 500B, 500C,
500D,
and 500E. Meters 500A, 500B, 500C, 500D, and 500E each determine 608
whether the transmitted identification number corresponds to the
identification
number stored in memory 54 of each meter. If the transmitted identification
number
matches the unique identification number stored in a meter, a transmit line of
modem unit 50 of the meter matching the identification number is enabled 610
and
transmit lines of modem units of all non-matching meters are disabled 612. For
example, if the identification number matches the identification number of
meter
500C, the modem unit transmit lines of meters 500A, 500B, 500D, and 500E will
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be disabled. After information is exchanged between central computer 58 and
enabled meter 500C, meters 500A, 500B, 500C, 500D, and 500E monitor 606 the
next incoming message. This routine continues until central computer 58
terminates the call and hangs up.
In addition, the master/slave configuration allows meters 500A, 500B, 500C,
500D, and 500E to initiate a call to central computer 58 as described above
using
meter 10. Specifically, upon detecting a condition 106, one of meters 500A,
500B,
500C, 500D, and 500E initiates the call to central computer 58. In one
embodiment, meters 500A, 500B, 500C, 500D, and 500E are configured so that
each meter has a unique valid range for timer circuit 80 parameters and
schedule
time valid range. For example, to prevent meters 500A, 500B, 500C, 500D, and
500E from originating calls without interrupting each other, meters 500A,
500B,
500C, 500D, and 500E can be programmed to initiate calls only during a
specific
time window, e.g., meter 500A, 10:00AM - 10:15 AM on 10/21/98, meter 500B,
10:16 AM - 10:30 AM on 10/22/98, 500C, 10:45 AM - 10:59 AM on 10/22/98
500D, 10:16 AM - 10:30 AM on 10/23/98 and 500E, 10:16 AM - 10:30 AM on
10/24/98. Each meter has a unique time window for originating the call to
central
computer 58.
Further, for events likely to occur simultaneously all meters within a the
group, or cluster, e.g., a power failure, meters 500A, 500B, 500C, 500D, and
500E
can be configured so that only one meter originates a call to central computer
58.
Specifically, an initiate call parameter can programmed into modem unit 50 so
that
microcomputer 52 is disabled from initiating call to central computer 58.
The above described modem unit exchanges information between the meter
and the central computer upon the occurrence of a condition within the meter.
The
modem unit microcomputer then evaluates the condition against parameters
stored in
memory 54. Using additional parameters, the microcomputer can then determine
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whether the information should be exchanged between the central computer and
the
meter. Also, the modem unit is configured to determine the proper time for
exchanging the information between the central computer and the meter. Such
modem unit is believed to reduce the number of nuisance type calls to central
computer. Further, the modem unit is configured to allow the meter to remain
operational despite error type conditions.
While the invention has been described in terms of various specific
embodiments, those skilled in the art will recognize that the invention can be
practiced with modification within the spirit and scope of the claims.
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