Redundant thermocouple

• US 5,663,899 A
• Filed: 06/05/1995
• Issued: 09/02/1997
• Est. Priority Date: 06/05/1995
• Status: Expired due to Fees

• Current Assignee: Advanced Micro Devices, Inc.
• Original Assignee: Advanced Micro Devices SDN Berhad (Advanced Micro Devices, Inc.)
• Inventors: Taylor, James, Zvonar, John G.
• Primary Examiner(s): Voeltz, Emanuel T.
• Assistant Examiner(s): KEMPER, MELANIE A
• Application Number:
  US08/462,958
• Time in Patent Office: 820 Days
• Field of Search: 364/557, 364/575, 62/126, 236/15 BB, 374/179, 374/181, 374/182, 374/10, 374/112, 374/113, 205/782
• US Class Current: 702/130
• CPC Class Codes: G01K 15/00 Testing or calibrating of thermometers

Abstract

A temperature sensing system contains a plurality of thermocouple pairs which are connected to an interface. The interface contains a microprocessor and a memory and provides for fault tolerance within the system by comparing measurements from each thermocouple within a thermocouple pair to a predetermined threshold value. If the difference between the thermocouple readings is greater than the threshold value, a malfunction is identified and corrective action is taken. The system determines which thermocouple has malfunctioned by comparing the readings of each of the thermocouples to a projected value based on historical data contained in the memory. The thermocouple whose reading varies to the greatest degree from its associated projected value is identified as the malfunctioning thermocouple. The reading from the properly functioning thermocouple is then used to produce an output signal. A likely cause of the malfunction can also be identified by specifying a short when the malfunctioning thermocouple provides a temperature reading substantially below its projected value, and specifying an open when the malfunctioning thermocouple provides a temperature reading substantially greater than its projected value.

Claims

1. An interface between an output device and at least one thermocouple pair, the interface comprising a microprocessor receiving input signals from the thermocouple pair and providing an output signal to the output device in response to the input signals,

further comprising a memory storing a threshold value for the thermocouple pair, wherein the microprocessor receives a first input signal from a first thermocouple of the thermocouple pair, a second input signal from a second thermocouple of the thermocouple pair, and the threshold value from the memory, the microprocessor compares a difference between the first input signal and the second input signal to the threshold value, and the microprocessor transmits an average of the first input signal and the second input signal as the output signal to the output device if the difference between the first input signal and the second input signal is less than the threshold value.

2. An interface as recited in claim 1, wherein the memory further stores previous input signals from the thermocouples as historical data, the microprocessor references the historical data to project a value for each of the first and second thermocouples and identify which of the first input signal and the second input signal is closest in value to its corresponding projected value if the difference between the first input signal and the second input signal is greater than the threshold value, and the microprocessor transmits the value of the input signal from the identified thermocouple as the output signal to the output device if the difference between the first input signal and the second input signal is greater than the threshold value.

3. An interface as recited in claim 1, wherein the memory further stores previous input signals from the thermocouples as historical data, the historical data including thermocouple profiles for each of the thermocouples, the microprocessor references the historical data to project a value for each of the first and second thermocouples and identify which of the first input signal and the second input signal is closest in value to its corresponding projected value if the difference between the first input signal and the second input signal is greater than the threshold value, the microprocessor adjusts the value of the input signal from the identified thermocouple to compensate for a bias identified in the corresponding thermocouple profile, and the microprocessor transmits the adjusted value as the output signal to the output device if the difference between the first input signal and the second input signal is greater than the threshold value.

4. An interface between an output device and at least one thermocouple pair, comprising:

a microprocessor receiving input signals from the thermocouple pair and providing an output signal to the output device in response to the input signals; and

a memory connected to the microprocessor, the memory storing a threshold value for each thermocouple pair, the memory further storing previous input signals from the thermocouple pairs as historical data,

wherein the microprocessor references at least one of the threshold values and the historical data in the memory as part of the analysis of the input signals to produce the output signal, and

wherein the microprocessor receives, for each thermocouple pair, an input signal from each of a first thermocouple and a second thermocouple, the microprocessor compares a difference between the first thermocouple input signal and the second thermocouple input signal to the corresponding threshold value, and the microprocessor outputs an average of the first thermocouple input signal and the second thermocouple input signal to at least one of a furnace controller and a display if the difference between the first thermocouple input signal and the second thermocouple input signal is less than the corresponding threshold value.

5. An interface between an output device and at least one thermocouple pair, comprising:

a microprocessor receiving input signals from the thermocouple pair and providing an output signal to the output device in response to the input signals; and

a memory connected to the microprocessor, the memory storing a threshold value for each thermocouple pair, the memory further storing previous input signals from the thermocouple pairs as historical data,

wherein the microprocessor references at least one of the threshold values and the historical data in the memory as part of the analysis of the input signals to produce the output signal, and

wherein the microprocessor receives, for each thermocouple pair, an input signal from each of a first thermocouple and a second thermocouple, the microprocessor compares a difference between the first thermocouple input signal and the second thermocouple input signal to the corresponding threshold value, and the microprocessor consults the historical data to project a value for each of the first and second thermocouples and identify which of the first thermocouple input signal and the second thermocouple input signal is closest in value to its corresponding projected value if the difference between the first thermocouple input signal and the second thermocouple input signal is greater than the corresponding threshold value, the input signal from the identified thermocouple being output to at least one of a furnace controller and a display.

6. An interface between an output device and at least one thermocouple pair, comprising:

a microprocessor receiving input signals from the thermocouple pair and providing an output signal to the output device in response to the input signals; and

a memory connected to the microprocessor, the memory storing a threshold value for each thermocouple pair, the memory further storing previous input signals from the thermocouple pairs as historical data,

wherein the microprocessor references at least one of the threshold values and the historical data in the memory as part of the analysis of the input signals to produce the output signal, and

wherein the microprocessor receives, for each thermocouple pair, an input signal from each of a first thermocouple and a second thermocouple, the microprocessor compares a difference between the first thermocouple input signal and the second thermocouple input signal to the corresponding threshold value, and the microprocessor consults the historical data to project a value for each of the first and second thermocouples and identify which of the first thermocouple input signal and the second thermocouple input signal is furthest in value from its corresponding projected value if the difference between the first thermocouple input signal and the second thermocouple input signal is greater than the corresponding threshold value, the output signal being an alarm identifying the thermocouple furthest in value from its corresponding projected value.

7. A temperature sensing system comprising:

at least one thermocouple pair including a first thermocouple and a second thermocouple located within a corresponding zone of a temperature sensing area;

a microprocessor receiving input signals from the thermocouple pair and producing an output signal in response to the input signals;

a memory connected to the microprocessor, the memory storing a threshold value for the thermocouple pair; and

an output device connected to the microprocessor, the output device receiving the output signal from the microprocessor,

wherein the microprocessor receives a first input signal from a first thermocouple of the thermocouple pair, a second input signal from a second thermocouple of the thermocouple pair, and the threshold value from the memory, the microprocessor compares a difference between the first input signal and the second input signal to the threshold value, and the microprocessor outputs, as the output signal, an average of the first input signal and the second input signal if the difference between the first input signal and the second input signal is less than the threshold value.

8. A temperature sensing system as recited in claim 7, wherein the memory further stores previous input signals from the thermocouples as historical data, the microprocessor consults the historical data to project a value for each of the first and second thermocouples and identify which of the first input signal and the second input signal is closest in value to its corresponding projected value if the difference between the first input signal and the second input signal is greater than the threshold value, and the microprocessor outputs, as the output signal, the input signal from the identified thermocouple.

9. A temperature sensing system comprising:

a plurality of thermocouple pairs, each including a first thermocouple and a second thermocouple, distributed within a temperature sensing area, each thermocouple pair being within a corresponding zone in the temperature sensing area;

a microprocessor receiving input signals from the thermocouple pairs and producing an output signal based on an analysis of the input signals;

a memory connected to the microprocessor, the memory storing a threshold value for each thermocouple pair, the memory further storing previous input signals from the thermocouple pairs as historical data; and

an output device connected to the microprocessor, the output device receiving the output signal from the microprocessor,

wherein the microprocessor consults at least one of the threshold values and the historical data in the memory as part of the analysis of the input signals to produce the output signal,

wherein the microprocessor receives, for each thermocouple pair, an input signal from each of the first thermocouple and the second thermocouple, the microprocessor compares a difference between the first thermocouple input signal and the second thermocouple input signal to the corresponding threshold value, and the microprocessor outputs an average of the first thermocouple input signal and the second thermocouple input signal to at least one of a furnace controller and a display if the difference between the first thermocouple input signal and the second thermocouple input signal is less than the corresponding threshold value.

10. A temperature sensing system comprising:

a plurality of thermocouple pairs, each including a first thermocouple and a second thermocouple, distributed within a temperature sensing area, each thermocouple pair being within a corresponding zone in the temperature sensing area;

a microprocessor receiving input signals from the thermocouple pairs and producing an output signal based on an analysis of the input signals;

a memory connected to the microprocessor, the memory storing a threshold value for each thermocouple pair, the memory further storing previous input signals from the thermocouple pairs as historical data; and

an output device connected to the microprocessor, the output device receiving the output signal from the microprocessor,

wherein the microprocessor consults at least one of the threshold values and the historical data in the memory as part of the analysis of the input signals to produce the output signal,

wherein the microprocessor receives, for each thermocouple pair, an input signal from each of the first thermocouple and the second thermocouple, the microprocessor compares a difference between the first thermocouple input signal and the second thermocouple input signal to the corresponding threshold value, and the microprocessor consults the historical data to project a value for each of the first and second thermocouples and identify which of the first thermocouple input signal and the second thermocouple input signal is closest in value to its corresponding projected value if the difference between the first thermocouple input signal and the second thermocouple input signal is greater than the corresponding threshold value, the input signal from the identified thermocouple being output to at least one of a furnace controller and a display.

11. A temperature sensing system comprising:

a plurality of thermocouple pairs, each including a first thermocouple and a second thermocouple, distributed within a temperature sensing area, each thermocouple pair being within a corresponding zone in the temperature sensing area;

a microprocessor receiving input signals from the thermocouple pairs and producing an output signal based on an analysis of the input signals;

a memory connected to the microprocessor, the memory storing a threshold value for each thermocouple pair, the memory further storing previous input signals from the thermocouple pairs as historical data; and

an output device connected to the microprocessor, the output device receiving the output signal from the microprocessor,

wherein the microprocessor consults at least one of the threshold values and the historical data in the memory as part of the analysis of the input signals to produce the output signal,

wherein the microprocessor receives, for each thermocouple pair, an input signal from each of the first thermocouple and the second thermocouple, the microprocessor compares a difference between the first thermocouple input signal and the second thermocouple input signal to the corresponding threshold value, and the microprocessor consults the historical data to project a value for each of the first and second thermocouples and identify which of the first thermocouple input signal and the second thermocouple input signal is furthest in value from its corresponding projected value if the difference between the first thermocouple input signal and the second thermocouple input signal is greater than the corresponding threshold value, the output signal being an alarm identifying the thermocouple furthest in value from its corresponding projected value.

12. A method of sensing and reporting a temperature value in a redundant thermocouple system, the method comprising the steps of:

(a) inputting a first temperature input signal from a first thermocouple and a second temperature input signal from a second thermocouple into a microprocessor;

(b) determining in the microprocessor a difference between the first temperature input signal and the second temperature input signal;

(c) comparing the difference determined in step (b) with a predetermined threshold value stored in a memory; and

(d) averaging in the microprocessor the first temperature input signal and the second temperature input signal and outputting the average as the temperature value if the result of step (c) is that the difference is less than or equal to the threshold value.

13. The method recited in claim 12, further comprising the step of:

(e) comparing the first temperature input signal to a first projected value corresponding to the first thermocouple and the second temperature input signal to a second projected value corresponding to the second thermocouple to determine which of the first and second temperature input signals is closest in value to its corresponding projected value and outputting a temperature signal representing the temperature input signal closest in value to its projected value if the result of step (c) is that the difference is greater than the threshold value.

14. A method as recited in claim 13, further comprising the step of issuing an alarm signal identifying the thermocouple whose temperature input signal is furthest from its corresponding projected value if the result of step (c) is that the difference is greater than the threshold value.

15. A method as recited in claim 13, further comprising the steps of updating historical data corresponding to the first thermocouple to include the first temperature input signal and updating historical data corresponding to the second thermocouple to include the second temperature input signal if the result of step (c) is that the difference is less than or equal to the threshold value.

16. A method as recited in claim 13, further comprising the step of updating historical data corresponding to the thermocouple whose temperature input signal is closest to its corresponding projected value if the result of step (c) is that the difference is greater than the threshold value.

17. The method recited in claim 12, further comprising the steps of:

(e) comparing the first temperature input signal to a first projected value corresponding to the first thermocouple and the second temperature input signal to a second projected value corresponding to the second thermocouple to determine which of the first and second temperature input signals is closest in value to its corresponding projected value if the result of step (c) is that the difference is greater than the threshold value;

(f) adjusting the temperature input signal identified in step (e) to compensate the identified temperature input signal for a corresponding bias; and

(g) outputting a temperature signal representing the value of the adjusted temperature input signal if the result of step (c) is that the difference is greater than the threshold value.