Current measurement

Patent metadata

Field	Value
Publication number	US-9939464-B2
Application number	US-201615099308-A
Country	US
Kind code	B2
Filing date	Apr 14, 2016
Priority date	Sep 12, 2011
Publication date	Apr 10, 2018
Grant date	Apr 10, 2018

Abstract

The present invention relates to current measurement apparatus 100. The current measurement apparatus 100 comprises a measurement arrangement 110, 114 which is configured to be disposed in relation to a load 108 which draws a current signal, the measurement arrangement being operative when so disposed to measure the load drawn current signal. The current measurement apparatus 100 also comprises a signal source 112 which is operative to apply a reference input signal to the measurement arrangement 110, 114 whereby an output signal from the measurement arrangement comprises a load output signal corresponding to the load drawn current signal and a reference output signal corresponding to the reference input signal. The current measurement apparatus 100 further comprises processing apparatus 116 which is operative to receive the output signal and to make a determination in dependence on the reference output signal and the load output signal, the determination being in respect of at least one of the load drawn current signal and electrical power consumed by the load.

First claim

The invention claimed is:

1. A current measurement apparatus comprising:
a first measurement arrangement configured to be disposed in a first current path, the measurement arrangement being operative when so disposed to measure the a current in the first current path;
a signal source operative to apply a reference input signal to the first measurement arrangement whereby a first output signal from the first measurement arrangement comprises a first signal corresponding to the current in the first current path and a reference output signal corresponding to the reference input signal;
a second measurement arrangement configured to be disposed in the first current path, the second measurement arrangement being operative when so disposed to measure the current in the first current path whereby a second output signal from the second measurement arrangement comprises a second signal corresponding to the current in the first current path; and
a circuit configured to form a difference between the second output signal and the first output signal and to provide the reference output signal.

2. The current measurement apparatus of claim 1 ,
wherein the first current path includes at least one of a power supply and a load.

3. The current measurement apparatus of claim 1 ,
wherein the first measurement arrangement includes a first shunt resistor; and
wherein the second measurement arrangement includes a second shunt resistor.

4. The current measurement apparatus of claim 1 ,
wherein the first measurement arrangement includes a first shunt resistor coupled in series with a live conductor; and
wherein the second measurement arrangement includes a second shunt resistor coupled in series with the live conductor.

5. The current measurement apparatus of claim 1 ,
wherein the first measurement arrangement includes a first shunt resistor coupled in series with a DC conductor; and
wherein the second measurement arrangement includes a second shunt resistor coupled in series with the DC conductor.

6. The current measurement apparatus of claim 1 ,
wherein the first measurement arrangement includes a first shunt resistor; and
wherein the second measurement arrangement includes a transformer.

7. The current measurement apparatus of claim 1 ,
wherein the first measurement arrangement includes a first shunt resistor coupled in series with one of a live conductor and a neutral conductor; and
wherein the second measurement arrangement includes a transformer coupled in series with the other of the live conductor and the neutral conductor.

8. The current measurement apparatus of claim 1 further including:
an equalizer circuit configured to equalize the first and second output signals with respect to their amplitudes and phase.

9. The current measurement apparatus of claim 1 further including:
an equalizer circuit configured to equalize the first and second output signals with respect to their amplitudes and phase, wherein the equalizer circuit operates on the second output signal to equalize it to the first output signal with respect to amplitudes and phase.

10. The current measurement apparatus of claim 1 further including:
pre-processing circuitry configured to identify frequency components of the first and second output signals; and
an equalizer circuit configured to equalize the first and second output signals with respect to their amplitudes and phase.

11. The current measurement apparatus of claim 10 ,
wherein the pre-processing circuitry is configured to perform a frequency transformation of the first and second output signals.

12. The current measurement apparatus of claim 10 ,
wherein the pre-processing circuitry is configured to perform a Fast Fourier Transform (FFT) of the first and second output signals.

13. The current measurement apparatus of claim 1 further including:
pre-processing circuitry configured to identify frequency components of the first and second output signals;
a statistical analysis circuit operative to identify a frequency component which corresponds to the current flowing in the first current path and to analyze frequency components adjacent to a frequency component of the reference input signal; and
an equalizer circuit configured to equalize the first and second output signals with respect to their amplitudes and phase, based at least in part upon the identified frequency component that corresponds to the current signal and the analysis of frequency components adjacent to a frequency component of the reference input signal.

14. The current measurement apparatus of claim 1 further including:
an extraction circuit configured to remove the reference output signal from noise.

15. The current measurement apparatus of claim 1 further including:
an equalizer circuit configured to equalize the first and second output signals with respect to their amplitudes and phase; and
a combination circuit configured to combine the equalized first and second output signals.

16. The current measurement apparatus of claim 1 further including:
a compensation circuit to adjust the reference signal based at least in part upon temperature.

17. A current measurement apparatus comprising:
a first measurement arrangement configured to be disposed in a first current path, the measurement arrangement being operative when so disposed to measure a current in the first current path;
a signal source operative to apply a reference input signal to the first measurement arrangement whereby a first output first signal from the first measurement arrangement comprises a first signal corresponding to the current in the first current path and a reference output signal corresponding to the reference input signal;
a second measurement arrangement configured to be disposed in the first current path, the second measurement arrangement being operative when so disposed to measure the current in the first current path whereby a second output signal from the second measurement arrangement comprises a second signal corresponding to the current in the first current path;
pre-processing circuitry configured to identify frequency components of the first and second output signals;
a statistical analysis circuit operative to identify a frequency component which corresponds to the current flowing in the first current path and to analyze frequency components adjacent to a frequency component of the reference input signal,
an equalizer circuit configured to operate on the second output signal to equalize it to the first output signal with respect to amplitudes and phase, based at least in part upon the identified frequency component that corresponds to the current signal and the analysis of frequency components adjacent to a frequency component of the reference input signal phase; and
a circuit configured to form a difference between the equalized second output signal and the first output signal and to provide the reference output signal.

18. The current measurement apparatus of claim 17 further including:
a compensation circuit to adjust the reference signal based at least in part upon temperature.

19. The current measurement apparatus of claim 17 further including:
an extraction circuit configured to remove the reference output signal from noise.

20. The current measurement apparatus of claim 17 further including:
a combination circuit configured to combine the equalized second output signal and the first output signal.

21. A current measurement apparatus comprising:
a first me

Assignees

• Analog Devices Global

Inventors

• Wood Stephen James Martin
• Hurwitz Jonathan Ephraim David
• Danesh Seyed Amir Ali

Classifications

• G01R27/16

  Measuring impedance of element or network through which a current is passing from another source, e.g. cable, power line · CPC title

• G01R35/04

  of instruments for measuring time integral of power or current · CPC title

• G01R27/02

  Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant (by measuring phase angle only G01R25/00) · CPC title

• G01R19/02

  Measuring effective values, i.e. root-mean-square values · CPC title

• G01R22/068

  Arrangements for indicating or signaling faults · CPC title