Methods and systems for determining temperature of an object

• US 7,407,323 B2
• Filed: 02/03/2006
• Issued: 08/05/2008
• Est. Priority Date: 02/03/2006
• Status: Expired due to Fees

• Current Assignee: GE Thermometrics Inc (Amphenol Corporation)
• Original Assignee: GE Infrastructure Sensing Incorporated (General Electric Company)
• Inventors: Hutcherson, David R.
• Primary Examiner(s): VERBITSKY, GAIL KAPLAN
• Application Number:
  US11/347,712
• Publication Number:
  US 20070183475A1
• Time in Patent Office: 914 Days
• Field of Search: 374120-121, 374/1, 374/129, 374/2, 374/133, 600/474, 600/549, 702/2
• US Class Current: 374/1
• CPC Class Codes: G01J 5/16 Arrangements with respect to the cold junction; Compensating influence of ambient temperature or other variables

Abstract

Methods and systems for detecting a temperature T_O of a remote object are provided. The method includes storing in memory, a lookup table relating an output voltage of an infrared sensor to a temperature sensed by the infrared sensor V(T_O, T_A), determining a temperature sensor voltage output corresponding to a temperature T_A proximate the infrared sensor, determining a first voltage as a function of the temperature T_A proximate the infrared sensor and a reference temperature T_REF, V(T_A, T_REF), determining a second voltage as a function of the temperature of the object T_O and the reference temperature T_REF, V(T_O, T_REF) by combining the determined temperature sensor voltage output and the first voltage, and determining a temperature of the object T_O from the lookup table using the second voltage.

Claims

1. A method of detecting a temperature T_O of a remote object, said method comprising:

measuring an output of an infrared sensor directed toward the remote object at two temperatures of the remote object and a temperature T_A proximate the infrared sensor;

determining calibration coefficients S and B from the measured output at the two temperatures;

determining a voltage output of a temperature sensor, the voltage output corresponding to the temperature T_A, V(T_O, T_A);

generating a lookup table relating the output voltage of the infrared sensor to the temperature sensed by the infrared sensor, V(T_O, T_A) versus the temperature T_O of the object at a plurality of temperatures using the determined values of S and B;

storing the lookup table in a memory;

determining a temperature sensor voltage output corresponding to a temperature T_A proximate the infrared sensor;

determining a first voltage as a function of the temperature T_A proximate the infrared sensor and a reference temperature T_REF, V(T_A, T_REF);

determining a second voltage as a function of the temperature of the object T_O and the reference temperature T_REF, V(T_O, T_REF) by combining the determined temperature sensor voltage output and the first voltage; and

determining a temperature of the object T_O from the lookup table using the second voltage.

2. A method in accordance with claim 1 wherein a voltage output of the infrared sensor is given by V=S(T_O^B−

T_A^B), where

V=output voltage from thermopile,

T_O=object temperature in °

K

T_A=ambient temperature in °

K

S=sensitivity coefficient

B=calibration coefficient, and

wherein determining calibration coefficients S and B comprises;

measuring a first voltage output of the infrared sensor at a first temperature such that V₁=S(T_O^B−

T_A^B);

measuring a second voltage output of the infrared sensor at a second temperature such that V₂=S(T_A^B−

T_REF^B);

combining the first voltage output and the second voltage output such that V₂/V₁=(T_O^B−

T_A^B)/(T_A^B−

T_REF^B)

determining B using numerical iteration; and

determining S by solving V₁=S(T_O^B−

T_A^B) for S such that S=V1/(T_O^B−

T_A^B) using the measured value for V1 and the determined value for B.

3. A method in accordance with claim 1 wherein determining a first voltage, V(T_A, T_REF) comprises determining a first voltage V(T_A, T_REF) using V(T_A, T_REF)=S(T_O^B−

T_A^B).

4. A method in accordance with claim 1 wherein determining a second voltage, V(T_O, T_REF) comprises determining a second voltage, V(T_O, T_REF) using V(T_O, T_REF)=(T_O, T_A)+(T_A, T_REF).

5. A system for determining a temperature of a remote object comprising:

an infrared temperature sensor;

a temperature sensor configured to detect a temperature of the infrared sensor;

a memory comprising a lookup table comprising a plurality of data points that relate the temperature sensor voltage output corresponding to a temperature T_A proximate the infrared sensor, V(T_O, T_A) for infrared sensor outputs at a plurality of temperatures of the object and temperatures T_A proximate the infrared sensor; and

a processor communicatively coupled to said infrared temperature Sensor, temperature sensor, and memory wherein the processor is programmed to;

store in memory, a lookup table relating an output voltage of an infrared sensor to a temperature sensed by the infrared sensor V(T_O, T_A);

determine a voltage output of the temperature sensor that corresponds to a temperature T_A proximate the infrared temperature sensor;

determine a first voltage as a function of the temperature T_A proximate the infrared sensor and a reference temperature T_REF, V(T_A, T_REF);

determine a second voltage as a function of the temperature of the object T_O and the reference temperature T_REF, V(T_O, T_REF) by combining the determined temperature sensor voltage output and the first voltage; and

determine a temperature of the object T_O from the lookup table using the second voltage.

6. A system in accordance with claim 5 wherein a voltage output of the infrared sensor is given by V=S(T_O^B−

T_A^B), where

V=output voltage from thermopile,

T_O=object temperature in °

K

T_A=ambient temperature in °

K

S=sensitivity coefficient

B=calibration coefficient, and

wherein calibration coefficients S and B are determined by;

a measurement of a first voltage output of the infrared sensor at a first temperature such that V₁=S(T_O^B−

T_A^B);

a measurement of a second voltage output of the infrared sensor at a second temperature such that V₂=S(T_A^B−

T_REF^B);

a combination of the first voltage output and the second voltage output such that V₂/V₁=(T_O^B−

T_A^B)/(T_A^B−

T_REF^B)

a determination of B using numerical iteration; and

a determination of S by solving V₁=S(T_O^B−

T_A^B) for S such that S=V₁/(T_O^B−

T_A^B) using the measured value for V₁ and the determined value for B.

7. A system in accordance with claim 6 wherein the values of S and B to are used generate the lookup table of the output voltage of an infrared sensor to the temperature sensed by the infrared sensor, V(T_O, T_A) versus the temperature T_O of the object at a plurality of temperatures.

8. A system in accordance with claim 5 wherein the first voltage V(T_A, T_REF) is determined using V(T_A, T_REF)S(T_O^B- T_A^B).

9. A system in accordance with claim 5 wherein the second voltage, V(T_O, T_REF) is determined using V(T_O, T_REF)=(T_O, T_A)+(T_A, T_REF).

10. A system in accordance with claim 5 wherein said temperature sensor comprises at least one of a thermistor, a silicon temperature sensor, and an RTD.

11. A system in accordance with claim 5 wherein said infrared sensor comprises a thermopile.

12. A computer program embodied on a computer readable medium for detecting a temperature T_O of a remote object, said program comprising a code segment that:

stores in memory, a lookup table relating an output voltage of an infrared sensor to a temperature sensed by the infrared sensor V(T_O, T_A);

determines a temperature sensor voltage output corresponding to a temperature T_A proximate the infrared sensor;

determines a first voltage as a function of the temperature T_A proximate the infrared sensor and a reference temperature T_REF, V(T_A, T_REF) where V(T_A, T_REF)=S(T_O^B−

T_A^B);

determines a second voltage as a function of the temperature of the object T_O and the reference temperature T_REF, V(T_O, T_REF) by combining the determined temperature sensor voltage output and the first voltage;

determines a temperature of the object T_O from the lookup table using the second voltage; and

outputs the determined temperature,

where, T_O=object temperature in °

K

T_A=ambient temperature in °

K

S=sensitivity coefficient

B=calibration coefficient.

13. A computer program in accordance with claim 12 further comprising a code segment for generating the lookup table that:

measures the infrared sensor output at two temperatures of the object and the temperature T_A proximate the infrared sensor;

determines calibration coefficients S and B from the measured temperatures;

determines temperature sensor voltage output corresponding to a temperature T_A proximate the infrared sensor, V(T_O, T_A).

14. A computer program in accordance with claim 12 wherein a voltage output of the infrared sensor is given by V=S(T_O^B−

T_A^B), where

V=output voltage from thermopile,

T_O=object temperature in °

K

T_A=ambient temperature in °

K

S=sensitivity coefficient

B=calibration coefficient, and

the computer program further comprises a code segment for determining the calibration coefficients S and B that;

measures a first voltage output of the infrared sensor at a first temperature such that V₁=S(T_O^B−

T_A^B);

measures a second voltage output of the infrared sensor at a second temperature such that V₂=S(T_A^B−

T_REF^B);

combines the first voltage output and the second voltage output such that V₂/V₁=(T_O^B−

T_A^B)/(T_A^B−

T_REF^B)

determines B using numerical iteration; and

determines S by solving V₁=S(T_O^B−

T_A^B) for S such that S=V₁/(T_O^B−

T_A^B) using the measured value for V₁ and the determined value for B.

15. A computer program in accordance with claim 13 further comprising a code segment that generates the lookup table of the output voltage of an infrared sensor to the temperature sensed by the infrared sensor, V(T_O, T_A) versus the temperature T_O of the object at a plurality of temperatures using the determined values of S and B.

16. A computer program in accordance with claim 12 further comprising a code segment that determines a second voltage, V(T_O, T_REF) using V(T_O, T_REF)=(T_O, T_A)+(T_A, T_REF).