Method and apparatus for measuring electricity

• US 4,801,874 A
• Filed: 02/27/1987
• Issued: 01/31/1989
• Est. Priority Date: 02/27/1987
• Status: Expired due to Term

• Current Assignee: Landis+Gyr AG (Landis+Gyr Group AG)
• Original Assignee: Process Systems, Inc. (Crane Company)
• Inventors: Loeffler, Horst R.
• Primary Examiner(s): Eisenzopf, Reinhard J.
• Assistant Examiner(s): Nguyen, Vinh P.
• Application Number:
  US07/020,077
• Time in Patent Office: 704 Days
• Field of Search: 324/141, 324/142, 324/76, 340/637, 364/483, 364/481, 364/841
• US Class Current: 324/142
• CPC Class Codes: G01R 21/1271 Measuring real or reactive component, measuring apparent energy
• CPC Class Codes: G01R 21/1331 Measuring real or reactive component, measuring apparent energy

Abstract

The method and apparatus disclosed relates to the electronic measurement of the electricity used by a load. The apparatus generates a rectified voltage signal proportional to the load voltage. A frequency modulated pulse train is generated in response to the load voltage signal, with the frequency of the pulses being proportional to the instantaneous amplitude of the rectified load voltage. A load current signal is generated that is proportional to the load current. A logic circuit gates the load current signal during each pulse of the frequency modulated pulse train to generate a signal representing the product of the instantaneous load voltage and the instantaneous load current. This signal from the logic means may be integrated over time to generate a signal representing the amount of electric energy used by the load. A method for practicing this invention is also disclosed.

Claims

1. Apparatus for electronically measuring the electricity used by a load comprising:

(a) means for generating an analog load voltage signal proportional to the instantaneous load voltage, said means being responsive to any positive and negative portions of the load voltage;

(b) means for generating a frequency modulated pulse train of signals in response to the load voltage signal, the instantaneous frequency of the pulses being proportional to the instantaneous amplitude of the load voltage signal;

(c) means for generating an analog load current signal proportional to the instantaneous load current, said means being responsive to any positive and negative portions of the load current; and

(d) logic means for gating the instantaneous load current signal during each pulse of the frequency modulated pulse train, said logic means generating an output signal comprising a train of pulses having a frequency proportional to the instantaneous load voltage and an amplitude proportional to the instantaneous load current, representing the product of the instantaneous load voltage and the instantaneous load current.

2. The apparatus of claim 1 wherein the means for generating a frequency modulated pulse train of signals comprises means for generating a train of uniform pulses, each pulse being substantially the same duration and substantially the same amplitude.

3. The apparatus of claim 1 wherein the means for generating a frequency modulated pulse train of signals comprises means for generating a train of unidirectional pulses.

4. The apparatus of claim 1 wherein the means for generating an analog load voltage signal comprises means for generating a rectified load voltage signal proportional to the instantaneous load voltage in response to an input voltage signal having positive and negative portions, and said means for generating a frequency modulated pulse train of signals is responsive to the rectified load voltage signal.

5. The apparatus of claim 1 further including zero crossing means for determining a change in the sign of the load voltage and providing a representative signal to the logic means.

6. The apparatus of claim 5 wherein the logic means is responsive to the zero crossings of the load voltage and the signal representing the amount of electric energy used.

7. The apparatus of claim 1 wherein the means for generating a load current signal comprises means for selectively providing either a positive or negative signal having an amplitude proportional to the amplitude of the load current, the amplitude the load current signal being negative only when one of the load voltage or load current is negative.

8. The apparatus of claim 1 wherein the means for generating a load current signal comprises:

means for providing a positive signal proportional to the amplitude of the load current;

means for providing a negative signal proportional to the amplitude of the load current; and

switch means for transmitting either the positive signal or negative signal in response to a received logic signal.

9. The apparatus of claim 8 wherein the switch means comprises an analog gate.

10. The apparatus of claim 8 wherein the switch means is responsive to a signal from said logic means.

11. The apparatus of claim 8 wherein the switch means comprises means for transmitting either the positive signal or negative signal in response to a predetermined logical combination of signals representing the zero crossing of the loading voltage and the amount of electric energy used.

12. The apparatus of claim 1 further comprising means for integrating over time the output signal representing the product of the instantaneous load voltage and the instantaneous load current to generate a signal representing the amount of electric energy used by the load.

13. The apparatus of claim 12 wherein the means for integrating comprises an up-down integrator.

14. The apparatus of claim 13 wherein the up-down integrator comprises means for integrating up or down in response to a predetermined logical combination of signals representing the zero crossing of the load voltage and the amount of electric energy used.

15. The apparatus of claim 12 further comprising comparator means for generating a signal when the signal representing the amount of electric energy used by the load has reached a predetermined level.

16. Apparatus for electronically measuring the electricity at a load comprising:

(a) means for generating a first analog load electric signal proportional to an instantaneous load condition, said means being responsive to any positive and negative portions of the load condition;

(b) means for generating a frequency modulated pulse train of signals in response to the first analog signal, the instantaneous frequency of the pulses being proportional to the instantaneous amplitude of the first analog signal;

(c) means for generating a second analog load electric signal, and

(d) logic means for gating the instantaneous second analog signal during each pulse of the frequency modulated pulse train to generate an output signal, said output signal comprising a train of pulses having a frequency proportional to the instantaneous first signal and an amplitude proportional to the instantaneous second signal, representing the product of the instantaneous first signal and the instantaneous second signal.

17. The apparatus of claim 16 wherein the means for generating a first analog signal comprises means for generating an analog load voltage proportional to an instantaneous load voltage.

18. The apparatus of claim 16 wherein the means for generating a first analog signal comprises means for generating an analog load signal proportional to an instantaneous load voltage.

19. The apparatus of claim 16 wherein the means for generating a first analog signal comprises means for generating an analog signal having a predetermined phase shift from the instantaneous load condition.

20. The apparatus of claim 16 wherein the means for generating a first analog signal comprises means for generating a signal dependent upon temperature.

21. The apparatus of claim 16 wherein the means for generating a second analog signal comprises means for generating an analog load current signal proportional to an instantaneous load current.

22. The apparatus of claim 16 wherein the means for generating a second analog signal comprises means for generating a constant amplitude signal.

23. The apparatus of claim 16 wherein the means for generating a second analog signal comprises means for generating a signal equivalent in amplitude to the first signal.

24. A method of electronically measuring the electricity used by a load, the method comprising:

(a) generating an analog load voltage signal in response to an input voltage signal proportional to the instantaneous load voltage and any positive and negative portions of the load voltage;

(b) generating a frequency modulated pulse train signal in response to the load voltage signal, the instantaneous frequency of the pulses being proportional to the instantaneous amplitude of the load voltage signal;

(c) generating an analog load current signal proportional to the instantaneous load current and any positive and negative portions of the load current; and

(d) gating the instantaneous load current signal during each pulse of the frequency modulated pulse train to generate an output signal, said output signal comprising a train of pulses having a frequency proportional to the instantaneous load voltage and an amplitude proportional to the instantaneous load current, representing the product of the instantaneous load voltage and the instantaneous load current.

25. The method of claim 24 further comprising the step of integrating the output signal over time to generate a signal representing the amount of electric energy used by the load.

26. The method of claim 25 wherein the step of integrating the output signal over time comprises the step of integrating up or down.

27. The method of claim 26 wherein the step of integrating up or down comprises integrating up or down in response to a predetermined logical combination of signals representing the zero crossing of the load voltage and the amount of electric energy used.

28. The method of claim 24 wherein the step of generating a frequency modulated pulse train of signals comprises generating a train of uniform pulses, each pulse having substantially the same duration and substantially the same amplitude.

29. The method of claim 24 wherein the step of generating a frequency modulated pulse train of signals comprises generating a train of unidirectional pulses.

30. The method of claim 24 wherein the step of generating an analog load voltage signal comprises generating a rectified load voltage signal proportional to the instantaneous load voltage in response to an input voltage signal having positive and negative portions, and the step of generating a frequency modulated pulse train of signals comprises generating a frequency modulated pulse train of signals in response to the rectified load voltage signal.

31. The method of claim 24 wherein the step of generating a load current signal comprises transmitting either a positive or negative load current signal having an amplitude proportional to the amplitude of the load current in response to the receipt of a logical combination of signals representing the zero crossing of the load voltage and the amount of electric energy used.

32. The method of claim 24 wherein the step of gating the load current signal comprises transmitting either a positive or negative load current signal having an amplitude proportional to the amplitude of the load current in response to the receipt of a logical combination of signals representing the zero crossing of the load voltage and the amount of electric energy used.

33. The method of claim 24 wherein the step of generating a load current signal comprises selectively providing either a positive or negative load current signal having an amplitude proportional to the amplitude of the load current, and providing a negative load current signal only when one of the load voltage or load current is negative.