Multi-sensor configuration for non-contact voltage measurement devices

Patent metadata

Field	Value
Publication number	US-10551416-B2
Application number	US-201815974990-A
Country	US
Kind code	B2
Filing date	May 9, 2018
Priority date	May 9, 2018
Publication date	Feb 4, 2020
Grant date	Feb 4, 2020

Abstract

Systems and methods for measuring AC voltage of an insulated conductor are provided, without requiring a galvanic connection between the conductor and a test electrode or probe. A non-galvanic contact (or “non-contact”) voltage measurement system includes a sensor subsystem, an internal ground guard and a reference shield. A common mode reference voltage source is electrically coupled between the internal ground guard and the reference shield to generate an AC reference voltage which causes a reference current to pass through the conductive sensor. Control circuitry receives a signal indicative of current flowing through the sensor subsystem due to the AC reference voltage and the AC voltage in the insulated conductor, and determines the AC voltage in the insulated conductor based at least in part on the received signal. The sensor subsystem includes at least two independent sensors that are used to compensate for conductor position while improving accuracy and dynamic range.

First claim

The invention claimed is:

1. A device to measure alternating current (AC) in an insulated conductor, the device comprising:
a housing;
a sensor subsystem physically coupled to the housing, the sensor subsystem selectively positionable proximate the insulated conductor without galvanically contacting the conductor, wherein the sensor subsystem capacitively couples with the insulated conductor, the sensor subsystem comprising a first sensor portion and a second sensor portion independent from the first sensor portion;
a conductive internal ground guard which at least partially surrounds the sensor subsystem and is galvanically isolated from the sensor subsystem, the internal ground guard sized and dimensioned to shield the sensor subsystem from stray currents;
a conductive reference shield which surrounds at least a portion of the housing and is galvanically insulated from the internal ground guard, the conductive reference shield sized and dimensioned to reduce currents between the internal ground guard and an external ground;
a common mode reference voltage source which, in operation, generates an alternating current (AC) reference voltage having a reference frequency, the common mode reference voltage source electrically coupled between the internal ground guard and the conductive reference shield;
input voltage signal conditioning circuitry selectively alternatingly coupleable to the first sensor portion and the second sensor portion of the sensor subsystem, wherein the input voltage signal conditioning circuitry, in operation, generates a sensor current signal indicative of current conducted through the sensor subsystem due to the input voltage of the insulated conductor under test;
reference signal conditioning circuitry selectively alternatingly coupleable to the first sensor portion and the second sensor portion of the sensor subsystem, wherein the reference signal conditioning circuitry, in operation, generates a sensor current signal indicative of current conducted through the sensor subsystem due to the AC reference voltage detected in the insulated conductor under test; and
control circuitry communicatively coupled to the input voltage signal conditioning circuitry and the reference signal conditioning circuitry, wherein, in operation, the control circuitry:
receives sensor current signals from each of the input voltage signal conditioning circuitry and the reference signal conditioning circuitry; and
determines the AC voltage in the insulated conductor based at least in part on the received sensor current signals, the AC reference voltage, and the reference frequency.

2. The device of claim 1 , wherein the first sensor portion comprises a first plurality of spaced apart conductive sensors electrically coupled together, and the second sensor portion comprises a second plurality of spaced apart conductive sensors electrically coupled together.

3. The device of claim 2 , wherein the first plurality of conductive sensors of the first sensor portion are interleaved with the second plurality of conductive sensors of the second sensor portion.

4. The device of claim 1 , wherein the input voltage signal conditioning circuitry is selectively alternatingly coupleable to the first sensor portion and the second sensor portion via a first switch, and wherein the reference signal conditioning circuitry is selectively alternatingly coupleable to the first sensor portion and the second sensor portion via a second switch.

5. The device of claim 4 , wherein the control circuitry, in operation, controls the states of the first and second switches synchronously to alternatingly:
electrically couple the first sensor portion to the reference signal conditioning circuitry, and electrically couple the second sensor portion to the input voltage signal conditioning circuitry; and
electrically couple the second sensor portion to the reference signal conditioning circuitry, and electrically couple the first sensor portion to the input voltage signal conditioning circuitry.

6. The device of claim 5 , wherein the control circuitry, in operation, controls the states of the first and second switches synchronously at a 50 percent duty cycle.

7. The device of claim 1 , wherein the control circuitry, in operation:
determines which of the first sensor portion and the second sensor portion generates the largest sensor current signals; and
determines the AC voltage in the insulated conductor based at least in part on the determination of which of the first sensor portion and the second sensor portion generates the largest sensor current signals.

8. The device of claim 7 , wherein the control circuitry, in operation:
determines which of the first sensor portion and the second sensor portion generates the largest sensor current signals;
ignores the sensor current signals obtained from the one of the first and second sensor portions that generates the smallest sensor current signals; and
determines the AC voltage in the insulated conductor based at least in part on the sensor current signals obtained from the one of the first and second sensor portions that generates the largest sensor current signals.

9. The device of claim 1 , wherein the control circuitry, in operation:
determines a weighted combination of the received sensor current signals received from the input voltage signal conditioning circuitry and the reference signal conditioning circuitry; and
determines the AC voltage in the insulated conductor based at least in part on the weighted combination of the received sensor current signals.

10. The device of claim 1 , wherein the weighted combination of the received sensor current signals comprises at least one of a linearly weighted combination or an exponentially weighted combination.

11. The device of claim 1 wherein each of the input voltage signal conditioning circuitry and the reference signal conditioning circuitry comprises at least one of an amplifier, a filter, or an analog-to-digital converter.

12. The device of claim 1 wherein the input voltage signal conditioning circuitry is optimized to condition or process input voltage signals, and the reference signal conditioning circuitry is optimized to condition or process AC reference voltage signals.

13. The device of claim 1 wherein the sensor subsystem and the conductive internal ground guard are each non-planar in shape.

14. The device of claim 1 wherein the control circuitry obtains a first measurement when the common mode reference voltage source is disabled, obtains a second measurement when the common mode reference voltage source is enabled, and determines the AC voltage in the insulated conductor based at least in part on the first and second measurements, the AC reference voltage and the reference frequency.

15. A method of operating a device to measure alternating current (AC) voltage in an insulated conductor, the device comprising a housing, a sensor subsystem physically coupled to the housing, the sensor subsystem selectively positionable proximate the insulated conductor without galvanically contacting the conductor, wherein the sensor subsystem capacitively couples with the insulated conductor, the sensor subsystem comprising a first sensor portion and a second sensor portion independent from the first sensor portion, a conductive internal ground guard which at least partially surrounds the sensor subsystem and is galvanically isolated from the sensor subsystem, the internal ground guard sized and dimensioned to shield the sensor subsystem from stray currents, and a conductive reference shield which surrounds at least a portion of the housing and is

Assignees

• Fluke Corp

Inventors

• Steuer Ronald
• Rodriguez Ricardo

Classifications

• G01R15/16

  using capacitive devices · CPC title

• G01R19/0084

  Measuring voltage only · CPC title

• G01R1/04 Primary

  Housings; Supporting members; Arrangements of terminals · CPC title

• G01R15/12

  Circuits for multi-testers {, i.e. multimeters}, e.g. for measuring voltage, current, or impedance at will · CPC title

• G01R19/155

  Indicating the presence of voltage · CPC title