Intelligent electronic device having circuitry for noise reduction for analog-to-digital converters

• US 7,916,060 B2
• Filed: 12/19/2008
• Issued: 03/29/2011
• Est. Priority Date: 01/27/2005
• Status: Active Grant

• Current Assignee: EI Electronics LLC (Hubbell, Inc.)
• Original Assignee: Electro Industries/Gaugetech
• Inventors: Zhu, Hai, Spanier, Joseph
• Primary Examiner(s): Jeanglaude; Jean B
• Application Number:
  US12/339,825
• Publication Number:
  US 20090096654A1
• Time in Patent Office: 830 Days
• Field of Search: 341/123, 341/156, 341/155, 341117-120
• US Class Current: 341/155
• CPC Class Codes: H03M 1/0682 using a differential network structure, i.e. symmetrical with respect to ground
• CPC Class Codes: H03M 1/12 Analogue/digital converters H03M1/001 – H03M1/10 take precedence

Abstract

An intelligent electronic device (IED), e.g., an electrical power meter, having circuitry for an input structure of an analog-to-digital converter (ADC) that reduces noise of a signal from a sensor in the device, resulting in a highly accurate power measurement, is provided. The circuitry includes a first single-ended analog-to-digital converter with an input from a voltage signal and a second single-ended analog-to-digital converter with an input that is the reference voltage used by the voltage signal. A programmable device subtracts the digital output of the second single-ended analog-to-digital converter from the digital output of the first single-ended analog-to-digital converter to produce a digital result of the voltage signal that is free from common-mode noise.

Claims

1. A hybrid-differential analog-to-digital converter, comprising:

a first single-ended analog-to-digital converter having a first input from a voltage signal;

a second single-ended analog-to-digital converter having a second input from a signal ground wherein said signal ground is a first reference voltage for said voltage signal; and

a programmable device in communication with a first output of said first single-ended analog-to-digital converter and a second output of said second single-ended analog-to-digital converter, said programmable device provides a digital result that is said second output subtracted from said first output, wherein said digital result is free from common-mode noise, wherein said voltage signal corresponds to an output from a sensor coupled with said hybrid-differential analog-to-digital converter and said first reference voltage is a sensor ground of said sensor.

2. The hybrid-differential analog-to-digital converter of claim 1, wherein said programmable device compensates for discrepancies between said first single-ended analog-to-digital converter and said second single-ended analog-to-digital converter.

3. The hybrid-differential analog-to-digital converter of claim 1, wherein said first single-ended analog-to-digital converter and said second single-ended analog-to-digital converter have a common ground and a common reference voltage.

4. The hybrid-differential analog-to-digital converter of claim 1, wherein said first single-ended analog-to-digital converter and said second single-ended analog-to-digital converter are configured to sample said voltage signal and said signal ground simultaneously.

5. The hybrid-differential analog-to-digital converter of claim 1, wherein said first single-ended analog-to-digital converter and said second single-ended analog-to-digital converter have similar direct current and alternating current performance.

6. The hybrid-differential analog-to-digital converter of claim 1, wherein said programmable device is a Field Programmable Gate Array.

7. The hybrid-differential analog-to-digital converter of claim 1, wherein said programmable device is a Complex Programmable Logic Device.

8. The hybrid-differential analog-to-digital converter of claim 1, wherein said programmable device is a microcontroller.

9. A method for reducing noise in an intelligent electronic device, comprising:

inputting a voltage signal into a first single-ended analog-to-digital converter, the voltage signal being generated by a sensor sensing a voltage across a load;

inputting a signal ground of the sensor into a second single-ended analog-to-digital converter wherein said signal ground is a first reference voltage of said voltage signal; and

subtracting a second digital output of said second single-ended analog-to-digital converter from a first digital output of said first single-ended analog-to-digital converter wherein said second digital output corresponds to said signal ground and said first digital output corresponds to said voltage signal, said subtracted result is free from common-mode noise.

10. The method of claim 9, further comprising:

prior to said step of subtracting, adding first gain compensation to said first digital output and adding second gain compensation to said second digital output wherein said first gain compensation and said second gain compensation compensate for discrepancies between said first single-ended analog-to-digital converter and said second single-ended analog-to-digital converter.

11. The method of claim 9, wherein said first single-ended analog-to-digital converter and said second single-ended analog-to-digital converter have a common ground and a common reference voltage.

12. The method of claim 9, wherein said first single-ended analog-to-digital converter and said second single-ended analog-to-digital converter are configured to sample said voltage signal and said signal ground simultaneously.

13. The method of claim 9, wherein said first single-ended analog-to-digital converter and said second single-ended analog-to-digital converter have similar direct current and alternating current performance.

14. The method of claim 9, wherein said step of subtracting is performed by a programmable device.

15. A revenue meter for determining power consumed in an electrical distribution system, comprising:

a potential transformer coupled to at least one phase of the electrical distribution system;

a first single-ended analog-to-digital converter coupled to the potential transformer for receiving a first signal indicative of a voltage on the at least one phase of the electrical distribution system;

a second single-ended analog-to-digital converter coupled to a signal ground of the potential transformer; and

at least one processing device coupled to the first and second single-ended analog-to-digital converters for receiving the first signal and the ground signal, subtracting the ground signal from the first signal to determine a noise-free voltage signal of the at least one phase of the electrical distribution system,

wherein the at least one processing device determines an amount of power consumed on the at least one phase of the electrical distribution system based on the noise free voltage signal.

16. An intelligent electronic device for determining power consumed in an electrical distribution system, comprising:

a sensor having a sensor output wherein said sensor senses a voltage across a load of at least one phase of the electrical distribution system;

a first single-ended analog-to-digital converter having a first input from a voltage signal wherein said voltage signal corresponds to said sensor output;

a second single-ended analog-to-digital converter having a second input from a signal ground of said sensor wherein said signal ground is a first reference voltage for said sensor;

a programmable device in communication with a first output of said first single-ended analog-to-digital converter and a second output of said second single-ended analog-to-digital converter, said programmable device provides a digital result that is said second output subtracted from said first output, wherein said digital output is free from common-mode noise; and

a processor that receives said digital result, determines a value for said voltage across said load and determines an amount of power consumed across said load.

17. The intelligent electronic device of claim 16, wherein said first single-ended analog-to-digital converter and said second single-ended analog-to-digital converter have a common ground and a common reference voltage.

18. The intelligent electronic device of claim 16, wherein said first single-ended analog-to-digital converter and said second single-ended analog-to-digital converter are configured to sample said voltage signal and said signal ground simultaneously.

19. The intelligent electronic device of claim 16, wherein said first single-ended analog-to-digital converter and said second single-ended analog-to-digital converter have similar direct current and alternating current performance.

20. The intelligent electronic device of claim 16, wherein said programmable device compensates for discrepancies between said first single-ended analog-to-digital converter and said second single-ended analog-to-digital converter.

21. The intelligent electronic device of claim 16, wherein said programmable device is a Field Programmable Gate Array.

22. The intelligent electronic device of claim 16, wherein said programmable device is a Complex Programmable Logic Device.

23. The intelligent electronic device of claim 16, wherein said programmable device is a microcontroller.

24. The intelligent electronic device of claim 16, wherein said first single-ended analog-to-digital converter and said second single-ended analog-to-digital converter are two channels of the same physical device.