Note: Descriptions are shown in the official language in which they were submitted.
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This invention can be related to measurement of
electrical energy, ~or exa~ple, ln volt-Joules or kilowatt-
hours. It accumulates such measurements and then when a
maximum accumula~ion has occurred a consistent and predict-
able event in the form of a pulse is generated. The input
to this device can be a low current function of the power
carried in a conductor conveying direct or alternating voltage
and the current function can be derived from a current
sensor. Such a current sensor may be a current transformer,
photocell, thermistor, solar cell, radiation sensor, direct
current sensor, microphone or other alternating or direct
current output sensing device.
Vnited States Patent 4,039,897 issued August 2, 1977
to J.E. Dragoset, discloses a system for controlling power
by sensing the power during a half cycle and to the provision
of output signals proportional to the voltage and current
across and to the load. The output signals are multiplied
and a resultant product signal is compared to a reference
signal and time integrated and fed to a pulse width modulator.
United States Patent 4,055,803 issued October 25, 1977
to Raymond L. Kraley, et al discloses a simultaneous watt
or VAR indicator and includes current and voltage trans-
formers and a modulator.
United States Patent ~,080,568 issued March 21, 1378
to L.L. ~unk discloses an energy monitor wherein a voltage/
proportional to the load current, is generated and conveyed
to a linear voltage controlled oscillator. A waveform
derived by a counter from timing pulses provided by an
electronic clock circuit gates the output of the VCO to a
counter, and also provides for alternation of a display
hetween a representation of energy consumed and time of day.
Se~ective adjustment of the ~oltage to frequency converting
circuit's gain provides an output indication in appropriate
electrical or monetary units. All gatin~ and resetting of
counters, display multiplexing and timekeeping functions
are provided by the electronic clock circuit. This patent
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disclQses only limited similarity with the present invention,
that is in the generation of a voltage proportional to the
load current and converts this voltage into a ~requency via
a voltage controlled oscillator. The pulse counting net-
work counts the number of waves generated and using a variably
set gated counter counts until "an event" is completed (ie
the total number of wave co~ts occurs). A pulse output
would then result in a single increment when the ~ave
counter resets to zero. On the other hand, the present
invention converts the voltage to a linear charging current
of an integrator. Then when an adequate amount of integration
occurs the total allowable system voltage (which can be
variably s~t via ~ presettable time base or variable integration
speed is achieved. Then the integrator is reset to a pre-
determined base voltage by the Schmitt trigger~ A pulse
results and again the display can be incremented.
In summary, the U.S. patent in question relies on a
voltage controlled oscillator and counter ~or accuracy,
whereas the "citameter" relies on a precision integrator
and Schmitt trigger for accuracy. That is how the two
circuits di~fer. The result is that the present invention
can perform the same result substantially more reliably,
with lower enqr~y consumption and in a more cost effective
manner.
The meter described in United States Patent 4,080,568
is most unsatisfactory since it relies on the linearity o~
the voltage controlled oscillator and such linear ~C
oscillators are extremely difficult to build. In addition,
the circuitry of the disclosure of this patent is complex,
expensive, re~uires high tolerance components and is not
susceptible to mass production.
United States Patent 4,224,671 issued September 23, 1980
to Fumio Sugiyama discloses an electronic watt hour meter
which again mulkiplies curren and ~oltage signal and
puls~-width modulates the voltage signal. The current
signals are integrated and the counter decodes and
establishes a display signal. This apparatus is merely a
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relatively complicated watt~hour meter which employs
arithmetic operation.
One object of the invention is to provide an accurate,
simple and inexpensive electrical Joule meter which over-
comes the deficiencies residing in the above-discussed
prior art.
Another object of the invention is ~o provide a Joule
meter which may be operated from signals derived from current
and voltage transformers, radiation sensors, heat or light
sensitive cells and microphones.
Another object of the invention is to provide a device
for measuring and accumulating energy consumption which
is reliable and portable and susceptible to the use of
integrated circuits.
Another object of the invention is to provide a device to
interface a signal current from a sensor with a computerized
monitoring device.
A preferred embodiment of ~he invention will now be
described with reference ~o the accompanying drawings in
which:
Fig. 1 is a block diagram of the circuit used in
the invention;
Fig. 2 is a circuit diagram of an example of a
sensorO Vsing this type of sensor the circuit diagram
displays the connection be ween a single phase mains voltage
source and a load, showing a current transformer connected
to one side of the line;
Fig. 3 is a circuit diagram of an absolute value
converter stage;
Fig. 4 is a circuit diagram of an analogue integrater
stage;
Fig. 5 is a circuit diagram of a Schmitt txigger stage;
Fig. 6 is a circuit diagram of an example of a pulse
counter and count accumulator to di~play interface, and
Fi~ 7 is a circuit diagram of the complete circuitry
of t~e device;
Referring to Fig. 1, the device is divided into
thre~ distinct sub-circuits compri ing a precision absolute
value converter 200, a pre~ision analogue integrator 400
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a Schmitt trigger 500. The input may be obtained ~rom a
current transformer (which will be used as an example in
this disclosure1 or other sensor. Fig. 2 shows the derivation
o~ a voltage ~1 to be applied the input of the circuit shown
in Fig. 1. A current transformer 20, having a single turn
primary coil 22 and a secon~ary coil 24, may have a l:N turns
ratio. The secondary coil 24 is terminated by a resistor
R301 (shown in Fig. 3) in an absolute value converter stage,
so that the output voltage is:
1 = (Ip - excitation current) R/N (The excitation
current is very small with respect to any registerable values
of Ip)~
Since it is intended that the device be used with
selected s~andard line voltage, i.e~ 115 volts, 220, 440, etc.,
the sensing of line current provides, with the line voltage,
a product which is proportional to the in-phase power
transmitted. Integration of the product, over a selected
period, provides a summation of the energy which may be in
Joules, watt-seconds, kilowatt-hours, foot-pound-seconds, etc.
Referring now to Fig. 3, the simplified circuit
diagram of an absolute value converter stage (200 in figure
1 is shown. The function of this stage is to take any
current Is whether it be positive or negati~e r generate a
proportional voltage on the positive input terminal of
operational amplifier 30 and cause a proportional (but
positive only) voltage across capacitor C302. Capacitor
C301, is used only to suppress high frequency line trans-
missions. Operational amplifier 30 is used as a standardizing
buffer and is not required for lower accuracy metering.
Operational amplifier 35 and its two f~edback diodes D301
and D302 do the actual absolute value converting. The
output of operational ampli~ier 30 is rectified then fed
back to its input to assure unity gain and i6 fed to the
absolute value converter stage output V2. The capacitor
C303 is to assure a no ripple d.c. output. The potentiometer
P301 trims the entire device for manufacturing tolerances~
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The precision integrator 400 in Fig. 1 will now be
described. Ref~rring now to Fig. 4, the output V2 from the
converter (20-0 in FigO 1~ is fed to an operational amplifier
40 via a resistor R408. The output from the integrator is
present across terminals VT and V3 and the capacitor C409
sets the time base of the integrator as follows:
R408.C409 = t
The integrator receives the voltage V2 and converts
it to a constant charging current through the capacitor C303
in Fig. 3. The value of the voltage at V3 lowers as the
capacitor C303 is charged and this changing voltage is
monitored by the Schmitt trigger, 500 in Fig. 1, now to
be described with reference to Fig. 5.
The output ~73 from ~he integrator, shown in Fig. 4, is
applied to an operational amplifier 550 via resistor R505.
The output of the operational ampli~ier 550 is fed to the
base of a transistor T501 via resistor R5090 The Schmitt
trigger circuit maintains a consistent time base. This is
accomplished by keeping V4 low until V3 is low enough
to be equal to V+~ Then V5 goes high causing the
transistor T501 to conduct. Since the capacitor C409 is
connected across VT and V3 (see Fig. 4) C409 is thereby
discharged as C303 discharges, V3 rises until preset
voltage is achieved internally in the Schmitt trigger. The
transistor T501 stops conducting as V4 goes low and the
process is repeated. V4 is also utilized to activate an
indicator.
Fig~ 6 shows the interface between the Schmitt trigger
output and a LC~ display 600. Although the display is
not part of the patent, the desired action would be: the
pulses V5 are applied to an integral pulse count and
accumulator 620 which may be an ICM 7224 (Manufactured by
Intexsil Inc.) The ICM 7224 provides 29 segment outpu s
and a backplane driver output, generating the zero d.c.
component signals necessary to drive a conventional 4 1/2
or less digit liquid crystal display 600~ This device
al50 includes a complete RC oscilla~or and divider chain to
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generate the backplane frequency. This device may be a
CM~S 4 l/2 digit counter including decoders, output latches,
display dri~ers and reset circuitry. In summary the ICM 7224
will take an input pulse, count and display the total number
of pulses presented to it.
Fi~. 7 is a circuit diagram of the three stages together,
using four standard operational amplifiers, a description is
deemed unnecessary~
Examples of applications of the subject invention:
a) A current transformer generating output resulting from
a.c. feeders, current would provide input for this
device which would in turn be processed through this
device so that once 313 Joules were accumulated, an
output pulse would be generated. Once one hundred of
these pulses have occurred at an average of 115
Volts one kilowatt hour has been measured,
b) A direct current sensing device resulting from a battery
and/or battery charging system would provide input for
this device ~hich would in turn be processed through
this device so that the number of Joules used or gen-
erated would be accumulated and the battery' 5 energy
level can be quantified, a charging system could be
turned on or off at a predetermined level which would
be a function of the amount of energy removing out of
that battery's potential energy capacity. Alternately,
after an appropriate energy level is indicated as used
by the invention, a modification of the current it is
monitoring to alternate supplies or uses, is possible.
c) A radiation sensor generating output resulting from
radioactive emissions would provide input for ~his
device which would in turn be processed by the inven-
tion so that the number of millirems is not only sensed
but also accumulated over time and the level of this
accumulation c~n be quantified and~or a resulting
reactiQn initiated.
d) A solar or photo cell generating output resulting from
light intensity ~ould provide input for the Electrical
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Joule Mete~ ~cc~eter and Indicator which would in
turn fie prQcessed ~y the E.J~M.A ~nd I so that the amount
of light o~er a ti~e period is accumulated for quantif-
icati~n and~or resulting action such as ending a photo-
grap~ic development process, turning off the lights in
a green~ouse, protection of a painting from the fading
process, etc.
e) A microphone generating output resulting from acoustic
pressure would provide input for the E.J.M.A &I whioh woul~
in turn be processed by the invention so that the amount
of acoustic pressure totalled over time (i.e. decibel
seconds~ could be quantified and a possible action
initiated such as, turning down the volume level, turning
off the noise-source (eg. machinery) could-be ini~iated
~efore serious ear or other damage resulted.
Further, because of the invention, the cost of measuring,
accumulating and triggering the xeaction is reduced, to
~t least l/lOth of alternative methods when it is used
in its integrated circuit form. Certainly, ~hrough the
use o~ combinations of other devices the accumulated
measurement of ~nergy used, in its various forms, is
possible. However, with the pres~nt inven~ion, similar
accuracy can ~e accomplished at extremely low cost with
increased reliaBility and portability due to the use of
~he limited number of discr~te, xeadily available,
components required. The ability to function accurately
with so few components is a result of the adapted
Schmitt trigger functioning for low level operation and
so will easily adapt itself to integrated circuit
operations, or
f) An interface for transferring signal current rom a
~ensor to a computerized monitoring device.
