Calibration system for voltage measurement devices

Patent metadata

Field	Value
Publication number	US-10502807-B2
Application number	US-201715695542-A
Country	US
Kind code	B2
Filing date	Sep 5, 2017
Priority date	Sep 5, 2017
Publication date	Dec 10, 2019
Grant date	Dec 10, 2019

Abstract

Systems and methods for calibrating a voltage measurement device are provided herein. The voltage measurement device generates a reference current signal and senses the reference current signal in a conductor under test. A calibration system may control a calibration voltage source to selectively output calibration voltages in a calibration conductor. The calibration system may obtain data from the voltage measurement device captured by the voltage measurement device when measuring the calibration conductor. Such data may include one or more reference current measurements, one or more voltage measurements, etc. The calibration system utilizes the obtained measurements to generate calibration data which may be stored on the voltage measurement device for use thereby during subsequent operation. The calibration data may include one or more lookup tables, coefficients for one or more mathematical formulas, etc.

First claim

The invention claimed is:

1. A calibration system operative to calibrate a voltage measurement device, wherein the voltage measurement device, in operation, generates a reference current signal and senses the reference current signal in a conductor under test via a voltage measurement device sensor, the calibration system comprising:
a controllable calibration voltage source operative to selectively output a voltage in a calibration conductor; and
control circuitry communicatively coupleable to the calibration voltage source and the voltage measurement device, wherein the control circuitry, in operation, for each calibration voltage of a plurality of calibration voltages:
controls the calibration voltage source to output the calibration voltage in the calibration conductor;
obtains a plurality of calibration points associated with the calibration voltage, each of the calibration points comprising:
a reference current signal data point obtained from the voltage measurement device that is indicative of the reference current signal that is measured by the voltage measurement device via the voltage measurement device sensor when the calibration voltage source outputs the calibration voltage in the calibration conductor; and
a calibration factor indicative of a ratio of the calibration voltage to a measured output voltage data point obtained from the voltage measurement device that is determined by the voltage measurement device based at least in part on the reference current signal data point;

determines calibration data for the voltage measurement device based on the obtained plurality of calibration points, the calibration data dependent on the reference current signal measured by the voltage measurement device and the plurality of calibration voltages; and
stores the calibration data on at least one nontransitory processor-readable storage medium associated with the voltage measurement device for use by the voltage measurement device during subsequent operation of the voltage measurement device.

2. The calibration system of claim 1 wherein the voltage measurement device is a non-contact measurement device, and for each of the plurality of calibration voltages, the calibration points comprises a range of reference current signal data points that are obtained by selectively adjusting a physical distance between the voltage measurement device sensor of the voltage measurement device and the calibration conductor.

3. The calibration system of claim 1 wherein the calibration data comprises a lookup table that, in operation, allows the voltage measurement device to determine a calibration factor for a particular reference current signal measurement and a particular output voltage measurement using bilinear interpolation.

4. The calibration system of claim 1 wherein the calibration data comprises coefficients for a plurality of mathematical formulas, wherein each of the plurality of mathematical formulas corresponds to a respective one of the calibration voltages.

5. The calibration system of claim 1 wherein, for each of the calibration voltages, the control circuitry determines the calibration data by fitting the plurality of calibration points to a curve defined by a mathematical formula.

6. The calibration system of claim 5 wherein, for each of the calibration voltages, the mathematical formula is y=a/(x−b) c +d, where y is the calibration voltage, x is the reference current signal, and a, b, c, and d are coefficients determined by analysis of the plurality of calibration points associated with the respective calibration voltage.

7. The calibration system of claim 6 wherein the value of the coefficients a, b, and c for each one of the plurality of mathematical formulas are equal to the value of the coefficients a, b, and c, respectively, for each of the other ones of the plurality of mathematical formulas.

8. The calibration system of claim 1 wherein the plurality of calibration voltages comprises at least three calibration voltages.

9. The calibration system of claim 1 wherein the voltage measurement device comprises a sensor array comprising a first sensor portion and a second sensor portion, the first sensor portion interleaved with the second sensor portion, and each of the first and second sensor portions are selectively coupleable to a signal current amplifier and a reference current amplifier via controllable switches.

10. The calibration system of claim 1 wherein the voltage measurement device comprises a sensor array comprising a plurality of sensor elements, and each of the sensor elements is selectively coupleable to an input node of processing circuitry and to a conductive guard node.

11. A calibration system operative to calibrate a voltage measurement device, the voltage measurement device comprising a plurality of voltage measurement device sensors and, in operation, the voltage measurement device generates at least one reference current signal and senses the at least one reference current signal in a conductor under test via the plurality of voltage measurement device sensors, the calibration system comprising:
a controllable calibration voltage source operative to selectively output a voltage in a calibration conductor; and
control circuitry communicatively coupleable to the calibration voltage source and the voltage measurement device, wherein the control circuitry, in operation:
controls the calibration voltage source to output a calibration voltage in the calibration conductor;
obtains a plurality of calibration points associated with the calibration voltage, each of the calibration points comprising:
a plurality of reference current signal data points obtained from the voltage measurement device that are indicative of the reference current signals that are measured by the voltage measurement device via the plurality of voltage measurement device sensors when the calibration voltage source outputs the calibration voltage in the calibration conductor; and
a calibration factor indicative of a ratio of the calibration voltage to a measured output voltage data point obtained from the voltage measurement device that is determined by the voltage measurement device based at least in part on the plurality of reference current signal data points;

determines calibration data for the voltage measurement device based on the obtained plurality of calibration points, the calibration data dependent on the reference current signals measured by the voltage measurement device via the plurality of voltage measurement device sensors; and
stores the calibration data on at least one nontransitory processor-readable storage medium associated with the voltage measurement device for use by the voltage measurement device during subsequent operation of the voltage measurement device.

12. The calibration system of claim 11 wherein the voltage measurement device is a non-contact measurement device, and at least some of the calibration points are obtained by selectively adjusting a physical distance between the voltage measurement device and the calibration conductor.

13. The calibration system of claim 11 wherein the calibration data comprises a lookup table that, in operation, allows the voltage measurement device to determine a calibration factor for a particular plurality of reference current signal measurements using interpolation.

14. The calibration system of claim 11 wherein the calibration data comprises coefficients for at least one mathematical formula.

15. The calibration system of claim 11 wherein the control circuitry determines the calibration data by fitting the calibration points to a curve defi

Assignees

• Fluke Corp

Inventors

• Steuer Ronald

Classifications

• G01R15/144

  Measuring arrangements for voltage not covered by other subgroups of G01R15/14 · CPC title

• G01D18/008

  with calibration coefficients stored in memory · CPC title

• G01R35/005 Primary

  Calibrating; Standards or reference devices, e.g. voltage or resistance standards, "golden" references (G01R33/0035, G01R35/002 take precedence) · CPC title

• G01R15/207

  Constructional details independent of the type of device used · CPC title

• G01R19/16561

  in hand-held circuit testers (see also G01R19/155) · CPC title