Methods and systems for determining temperature of an object

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 V 1 =S(T O B −T A B );

measuring a second voltage output of the infrared sensor at a second temperature such that V 2 =S(T A B −T REF B );

combining the first voltage output and the second voltage output such that V 2 /V 1 =(T O B −T A B )/(T A B −T REF B )

determining B using numerical iteration; and

determining S by solving V 1 =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 V 1 =S(T O B −T A B );

a measurement of a second voltage output of the infrared sensor at a second temperature such that V 2 =S(T A B −T REF B );

a combination of the first voltage output and the second voltage output such that V 2 /V 1 =(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 V 1 =S(T O B −T A B ) for S such that S=V 1 /(T O B −T A B ) using the measured value for V 1 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 V 1 =S(T O B −T A B );

measures a second voltage output of the infrared sensor at a second temperature such that V 2 =S(T A B −T REF B );

combines the first voltage output and the second voltage output such that V 2 /V 1 =(T O B −T A B )/(T A B −T REF B )

determines B using numerical iteration; and

determines S by solving V 1 =S(T O B −T A B ) for S such that S=V 1 /(T O B −T A B ) using the measured value for V 1 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 ).