System and method for identifying issues in current and voltage measurements

• US 8,396,680 B2
• Filed: 10/20/2008
• Issued: 03/12/2013
• Est. Priority Date: 10/20/2008
• Status: Active Grant

• Current Assignee: GM Global Technology Operations LLC (General Motors Company)
• Original Assignee: GM Global Technology Operations LLC (General Motors Company)
• Inventors: Katrak, Kerfegar K., Leutheuser, Andrew H.
• Primary Examiner(s): Teixeira Moffat, Jonathan C
• Assistant Examiner(s): BETSCH, REGIS J
• Application Number:
  US12/254,653
• Publication Number:
  US 20100100345A1
• Time in Patent Office: 1,604 Days
• Field of Search: 702/65, 361/88, 324/522
• US Class Current: 702/65
• CPC Class Codes: G01R 19/2509 Details concerning sampling, digitizing or waveform capturing
• CPC Class Codes: G01R 31/3842 combining voltage and current measurements

Abstract

First and second reference voltages are applied to first and second terminals of a processor via voltage divider circuits. First and second signal conditioning circuits are coupled to third and fourth terminals of the processor, respectively, and voltage or current sensors are coupled to the first and second signal conditioning circuits. The processor measures the electrical characteristics at the third and fourth terminals and computes first and second ratiometric values of the electrical characteristics, wherein the first ratiometric value is based upon a measurement obtained from the third terminal and the first reference voltage and the second ratiometric value is based upon a measurement of obtained from the fourth terminal and the second reference voltage. The processor further identifies an issue if a ratio of the first ratiometric value to the second ratiometric value exceeds a ratio of the first reference value to the second reference value.

Claims

1. A method of identifying issues associated with sensing of electrical characteristics of a sensed signal transmitted on an electrical conductor, wherein the method is performed in a processor having first, second, third and fourth terminals each representing separate input pins of the processor, the method comprising:

receiving a first reference voltage at the first terminal and a second reference voltage that is separately received at the second terminal, wherein the first and second reference voltages are references for measurement of the electrical characteristics that are received on separate input pins of the processor, and wherein the first and second reference voltages are substantially equal to each other and are substantially unchanging during normal operation;

obtaining first data about the electrical characteristics of the sensed signal from the third terminal and redundant second data about the electrical characteristics of the sensed signal from the fourth terminal, wherein the first data and the redundant second data both represent the measured electrical characteristics of the same sensed signal received on separate input pins of the processor that are separately electrically coupled to the electrical conductor transmitting the sensed signal;

computing, using the processor, a first computed value of the electrical characteristics of the sensed signal based upon the first data and the first reference voltage and a second computed value of the electrical characteristics based upon the second data and the second reference voltage;

determining, using the processor, a reference ratio of the first reference voltage received at the first terminal of the processor to the second reference voltage separately received at the second terminal of the processor, and a value ratio of the first computed value received at the third terminal of the processor to the second computed value received at the fourth terminal of the processor;

comparing the reference ratio to the value ratio using the processor; and

identifying an issue if the value ratio exceeds the reference ratio.

2. The method of claim 1 further comprising comparing the first and second computed values to each other, and identifying the issue if the first and second computed values differ.

3. The method of claim 2 further comprising comparing the first and second reference voltages to each other, and identifying the issue if the first and second computed values differ.

4. The method of claim 1 further comprising comparing the first and second reference voltages to each other, and identifying the issue if the first and second computed values differ.

5. The method of claim 1 wherein the identifying step comprises outputting a signal when the issue is identified.

6. The method of claim 1 wherein the first and second computed values of the electrical characteristics are computed ratiometrically.

7. The method of claim 1 wherein the electrical characteristics comprise a voltage measurement representing a voltage of the sensed signal.

8. The method of claim 1 wherein the electrical characteristics comprise a current measurement of the sensed signal.

9. The method of claim 8 wherein the first data about the current measurement and the second data about the current measurement are obtained from a common current sensor.

10. The method of claim 8 wherein the first data about the current measurement is obtained from a first current sensor and the second data about the current measurement is obtained from a second current sensor different from the first current sensor, wherein the first and second current sensors have different ranges of sensitivity.

11. The method of claim 10 wherein the determining of the value ratio comprises determining the ratio over the range of sensitivity associated with one of the first and second current sensors.

12. A method of diagnosing issues in sensing electrical characteristics of a sensed signal propagating in an electrical conductor, wherein the electrical characteristics comprise a current and a voltage of the same sensed signal measured by a processor having a plurality of terminals, the method comprising:

obtaining a first reference value, a second reference value, a first voltage measurement, a second voltage measurement, a first current measurement, and a second current measurement each on separate input pins of the processor, wherein the first and second voltage measurements represent the voltage of the same sensed signal and the first and second current measurements represent the current of the same sensed signal, wherein the first and second reference values are determined from reference voltages separately received on first and second input pins of the processor, and wherein the first and second voltage measurements and the first and second current measurements are each received on separate input pins of the processor that are each separately electrically coupled to the electrical conductor in which the sensed signal propagates;

computing, using the processor, a first value of the voltage based upon the first voltage measurement and the first reference voltage, a second value of the voltage based upon the second voltage measurement and the second reference voltage, a first value of the current based upon the first current measurement and the first reference voltage, and a second value of the current based upon the second current measurement and the second reference voltage;

using the processor, comparing the first reference value to the second reference value, and identifying an issue if the first and second reference values differ;

using the processor, comparing the first and second values of the voltage, and identifying the issue if the first and second values of the voltage differ;

using the processor, comparing the first and second values of the current, and identifying the issue if the first and second values of the current differ; and

using the processor, comparing a value ratio of the first and second voltages to a reference ratio of the first and second reference voltages, and identifying the issue in sensing the electrical characteristics of the sensed signal if the value ratio exceeds the reference ratio.

13. The method of claim 12 wherein the first value of the voltage and the first value of the current are each ratiometric values determined with respect to the first reference voltage, and wherein the second value of the voltage and the second value of the current are each ratiometric values determined with respect to the second reference voltage.

14. The method of claim 12 wherein the first and second values of are compared over a limited range.

15. A system for measuring an electrical characteristic of a sensed signal propagating in an electrical conductor, the system comprising:

a processor having a first terminal, a second terminal, a third terminal and a fourth terminal, wherein each of the first, second, third and fourth terminals are separate input pins of the processor;

a first reference voltage circuit configured to apply a first reference voltage to the first terminal of the processor, wherein the first reference voltage circuit comprises a first reduction resistor and a first sensing resistor configured as a voltage divider;

a second reference voltage circuit configured to apply a second reference voltage to the second terminal of the processor, wherein the second reference voltage circuit comprises a second reduction resistor and a second sensing resistor configured as a voltage divider, and wherein the first and second reference voltages represent reference values used in the measurement of the;

a first signal conditioning circuit electrically coupled to the electrical conductor to receive the sensed signal and to provide a first conditioned sensed signal to the third terminal of the processor; and

a second signal conditioning circuit separately electrically coupled to the electrical conductor to receive the sensed signal and to provide a second conditioned sensed signal to the fourth terminal of the processor;

wherein the processor is configured to separately measure the electrical characteristics of the same sensed signal using the first conditioned sensed signal received at the third terminal and using the second conditioned sensed signal received at the fourth terminal and wherein the processor is configured to compute first and second ratiometric values of the electrical characteristics of the sensed signal, wherein the first ratiometric value is based upon a measurement obtained from the third terminal and the first reference voltage and wherein the second ratiometric value is based upon a measurement obtained from the fourth terminal and the second reference voltage, and wherein the processor is further configured to identify an issue with the measuring of the electrical characteristics if a ratio of the first ratiometric value to the second ratiometric value exceeds a ratio of the first reference value to the second reference value.

16. The system of claim 15 wherein the resistances of the first and second reduction resistors are larger than the resistances of the first and second sensing resistors, respectively.

17. The system of claim 15 wherein the resistances of the first and second reduction resistors are at least twenty times greater than the resistances of the first and second sensing resistors, respectively.

18. The system of claim 15 further comprising a current sensor coupled to provide a current signal to the third and fourth terminals of the processor, and wherein the processor is further configured to measure the current signal at the third and fourth terminals and to compute first and second ratiometric values of the current signal, wherein the first ratiometric value of the current signal is based upon a measurement obtained from the third terminal and the first reference voltage and the second ratiometric value of the current signal is based upon a measurement of obtained from the fourth terminal and the second reference voltage, and wherein the processor is further configured to identify an issue if a ratio of the first ratiometric value of the current signal to the second ratiometric value of the current signal exceeds the ratio of the first reference value to the second reference value.

19. The system of claim 15 further comprising a first current sensor coupled to provide a first current signal to the third terminal of the processor and a second current sensor coupled to provide a second current signal to the fourth terminal of the processor, and wherein the processor is further configured to measure the first and second current signals at the third and fourth terminals, respectively, and to compute first and second ratiometric values of the current signal, wherein the first ratiometric value of the current signal is based upon a measurement obtained from the third terminal and the first reference voltage and the second ratiometric value of the current signal is based upon a measurement of obtained from the fourth terminal and the second reference voltage, and wherein the processor is further configured to identify an issue if a ratio of the first ratiometric value of the current signal to the second ratiometric value of the current signal exceeds the ratio of the first reference value to the second reference value.

20. The system of claim 19 wherein the first and second current signals are compared over a limited range.