Electrical signal measurement

Patent metadata

Field	Value
Publication number	US-9823275-B2
Application number	US-201414895868-A
Country	US
Kind code	B2
Filing date	May 30, 2014
Priority date	Jun 1, 2013
Publication date	Nov 21, 2017
Grant date	Nov 21, 2017

Abstract

The present invention relates to electrical measurement apparatus ( 10 ). The electrical measurement apparatus ( 10 ) comprises a measurement arrangement ( 20,24 ) configured to be disposed in relation to an electrical circuit ( 12,14,16,18 ) which bears an electrical signal, the measurement arrangement ( 20,24 ) being operative when so disposed to measure the electrical signal. The electrical measurement apparatus ( 10 ) further comprises a signal source ( 22 ) operative to apply a reference input signal to the measurement arrangement ( 20,24 ) whereby an output signal from the measurement arrangement comprises an electrical output signal corresponding to the electrical signal and a reference output signal corresponding to the reference input signal, the reference input signal having a substantially piecewise constant form which is repeated over each of plural cycles. The electrical measurement apparatus ( 10 ) yet further comprises processing apparatus ( 26 ) which is operative: to determine at least one cumulative representation, determination of the cumulative representation comprising summing plural received sections of the output signal, each of the plural received sections corresponding to at least a part and to a same part of the cycle of the reference input signal; and to determine at least one of: a transfer function for the measurement arrangement; a change in a transfer function for the measurement arrangement; and the electrical signal, in dependence on the at least one cumulative representation and the reference input signal.

First claim

The invention claimed is:

1. An apparatus configured to measure an electrical signal in an electrical circuit, the apparatus comprising:
a signal source configured to provide a reference input signal to a measurement circuit, wherein an output signal from the measurement circuit comprises an electrical output signal corresponding to the electrical signal and a reference output signal corresponding to the reference input signal, the reference input signal having a substantially piecewise form repeated over multiple cycles; and
a processing circuit configured to determine a cumulative representation indicative of the electrical signal by summing plural received sections of the output signal, each of the sections corresponding to at least a part of the cycle of the reference input signal.

2. The apparatus of claim 1 , wherein the electrical circuit bears a current signal, the measurement circuit is configured to measure the current signal and the electrical output signal comprised in the output signal corresponds to the current signal.

3. The apparatus of claim 2 , wherein the measurement circuit comprises a current sensor configured to measure the current signal and the signal source is configured to apply the reference input signal as a current.

4. The apparatus of claim 1 , wherein the electrical circuit bears a voltage signal, the measurement circuit is configured to measure the voltage signal and the electrical output signal comprised in the output signal corresponds to the voltage signal.

5. The apparatus of claim 4 , wherein the measurement circuit comprises a potential attenuator configured to measure the voltage signal and the signal source is configured to apply the reference input signal as a voltage.

6. The apparatus of claim 1 , wherein the processing circuit is further configured to determine a transfer function of the measurement circuit using the cumulative representation.

7. The apparatus of claim 1 , wherein the processing circuit configured to sum plural different parts of the cumulative representation and divide the summed plural parts by the number of parts to provide an averaged cumulative representation.

8. The apparatus of claim 6 , wherein the processing circuit is configured to determine the transfer function using less than a whole cycle of the reference input signal and the cumulative representation corresponds to less than a whole cycle of the reference input signal.

9. The apparatus of claim 6 , wherein the processing circuit is configured to determine the transfer function using a cumulative amplitude characteristic of the cumulative representation and a reference amplitude characteristic of the reference input signal.

10. The apparatus of claim 1 , wherein the processing circuit is further configured to determine a change in a transfer function for the measurement circuit using the cumulative representation.

11. The apparatus of claim 1 , wherein summing plural received sections of the output signal comprises summing corresponding subsections of the plural received sections, the corresponding subsections being selected using at least one of: pre-characterisation of behaviour of the measurement arrangement; and analysis of behaviour of the measurement arrangement during operation of the apparatus.

12. The apparatus of claim 6 , wherein the processing circuit is further configured to determine the transfer function using a part of the cycle of the reference input signal that includes a transition related variation.

13. The apparatus of claim 12 , wherein the processing circuit is further configured to apply different transfer function weighting for different respective parts of the cycle.

14. The apparatus of claim 6 , wherein the processing circuit is further configured to determine a time delay of at least one transition of the reference output signal relative to a respective at least one transition of the reference input signal, and wherein the processing circuit is configured to determine the transfer function using the time delay and at least one cumulative amplitude characteristic of the cumulative representation.

15. The apparatus of claim 1 , wherein the processing circuit is further configured to determine the cumulative representation on an ongoing basis wherein a first cumulative representation is determined by summing a first plurality of received sections of the output signal and a second cumulative representation is determined by summing a second plurality of received sections of the output signal, the second plurality of received sections comprising at least one more recently received section absent from the first plurality.

16. The apparatus of claim 1 , wherein the processing circuit is further configured to apply a windowing function to the output signal before determining the at least one cumulative representation.

17. The apparatus of claim 16 , wherein the windowing function is configured to attenuate an amplitude of the output signal corresponding to opposite ends of a window defined by the windowing function.

18. The apparatus of claim 16 , wherein the processing circuit is configured to determine the cumulative representation by summing corresponding ones of plural received sections of the output signal which overlap with each other, and wherein the processing circuit is configured to apply the windowing function to the overlapping received sections.

19. The apparatus of claim 6 , wherein the processing circuit is configured to scale the transfer function to compensate for scaling caused by at least one of: summing of the plural received sections of the output signal; and application of a windowing function to the output signal.

20. The apparatus of claim 1 , wherein the processing circuit is further configured to determine information about the electrical signal using the cumulative representation.

21. The apparatus of claim 1 , wherein the measurement circuit is further configured to measure the electrical signal in an absence of the reference input signal and wherein the processing circuit is configured to determine the cumulative representation after subtracting the measurement of the electrical signal measured in the absence of the reference input signal from the output signal.

22. The apparatus of claim 1 , wherein the processing circuit is further configured to remove the reference output signal from the output signal by subtracting the determined cumulative representation from the output signal.

23. The apparatus of claim 1 , wherein the reference input signal comprises at least one of: a pulse waveform; a bitstream having sections of highs and lows with different duty cycles; a staircase waveform; and a stepped waveform.

24. The apparatus of claim 1 , wherein the processing circuit is further configured to determine multiple cumulative representations indicative of the electrical signal, and wherein the processing circuit is further configured to identify at least one cumulative representation from the determined multiple cumulative representations that deviates from the other cumulative representations.

25. The apparatus of claim 1 , further comprising the measurement circuit, wherein the measurement circuit comprises a first and second sensors in a signal path that is configured to carry the electrical signal;
wherein one of the first and second sensors is configured to receive the electrical signal and the other of the first and second sensors is configured to receive the

Assignees

• Analog Devices Global

Inventors

• Danesh Seyed Amir Ali
• Holland William Michael James
• Stuart John
• Hurwitz Jonathan Ephraim David

Classifications

• G01R27/14

  Measuring resistance by measuring current or voltage obtained from a reference source (G01R27/16, G01R27/20, G01R27/22 take precedence) · CPC title

• G01R19/0084 Primary

  Measuring voltage only · CPC title

• G01R17/02

  Arrangements in which the value to be measured is automatically compared with a reference value · CPC title

• G01R19/2513

  Arrangements for monitoring electric power systems, e.g. power lines or loads; Logging · CPC title

• G01R19/0092

  Measuring current only · CPC title