SYSTEM FOR DETERMINING AMBIENT TEMPERATURE

• US 20090144014A1
• Filed: 12/04/2007
• Published: 06/04/2009
• Est. Priority Date: 12/04/2007
• Status: Active Grant

• Current Assignee: Ademco Inc. (Resideo Technologies, Inc.)
• Original Assignee: Honeywell International Inc.
• Inventors: Aljabari, Mohammad A.
• Granted Patent: US 8,280,673 B2
• Time in Patent Office: Days
• US Class Current: 702/130
• CPC Class Codes: G01K 1/20 Compensating for effects of temperature changes other than those to be measured, e.g. changes in ambient temperature
• CPC Class Codes: G01K 7/42 Circuits effecting compensation of thermal inertia; Circuits for predicting the stationary value of a temperature
• CPC Class Codes: G01K 7/427 Temperature calculation based on spatial modeling, e.g. spatial inter- or extrapolation
• CPC Class Codes: H05B 1/02 Automatic switching arrangements specially adapted to apparatus ; Control of heating devices thermally-actuated switches H01H37/00

Abstract

A mechanism for indicating ambient temperature of an enclosure from temperatures determined within the enclosure. The temperatures may be obtained from two or more sensors at each of two or more locations within the enclosure. The enclosure may include an apparatus inside such as electronics of which power consumption may be determined. Data including temperatures of two locations within the enclosure at various electronics power consumption levels may be entered into a 2-D plot. An approximation of the 2-D plot may be effected with an appropriate equation to be solved for ambient temperature. The data of the dimensional 2-D plot plus temperatures of a third location and air flow levels in the enclosure may be entered into a 3-D plot. An approximation of the 3-D plot may be effected with an appropriate equation to be solved for ambient temperature.

Claims

1. A method for determining ambient temperature comprising:

determining a first set of temperatures at a first location within an enclosure having an apparatus that may generate heat;

determining a second set of temperatures at a second location within the enclosure;

generating a two-dimensional relationship of the first and second sets of temperatures;

generating an equation as an approximation of the two-dimensional relationship; and

determining an ambient temperature proximate to the enclosure from the equation.

2. The method of claim 1, wherein the two-dimensional relationship of the first and second temperatures is generated from the first and second sets of temperatures determined approximately simultaneously at several levels of power consumed by the apparatus.

3. The method of claim 2, wherein:

the first set of temperatures at the several levels of power is represented as a first plot;

the second set of temperatures at the several levels of power is represented as a second plot; and

the first and second plots are combined into a third plot representing the first set of temperatures versus the second set of temperatures with a portion of the plots representing the several levels of the power dropping out.

4. The method of claim 3, further comprising:

generating the equation as an approximation of the third plot; and

solving for the ambient temperature from the equation.

5. The method of claim 4, wherein:

the equation is T_a=(T₁−

AT₂−

B)/(1−

A);

A is a slope of the third plot;

B is an offset of the third plot;

T₁ is a temperature at the first location; and

T₂ is a temperature at the second location.

6. The method of claim 5, wherein T₁ is greater than T₂ if heat is generated by the apparatus.

7. The method of claim 4, wherein:

the first set of temperatures is determined from one or more sensors at the first location;

the second set of temperatures is determined from one or more sensors at the second location;

temperatures from one or more sensors at the first location determined approximately simultaneously are averaged together as one temperature at the first location; and

temperatures from one or more sensors at the second location determined approximately simultaneously are averaged together as one temperature at the second location;

8. The method of claim 1, further comprising:

determining a third set of temperatures at a third location within the enclosure;

generating a three-dimensional relationship of the first, second and third set of temperatures;

generating a second equation as an approximation of the three-dimensional relationship; and

determining an ambient temperature proximate to the enclosure from the second equation.

9. The method of claim 8, wherein:

the first, second and third set of temperatures are determined approximately simultaneously at several levels of power consumed by the apparatus and at several levels of flow within the enclosure, which are represented as a three-dimensional plot having a first axis representing the first set of temperatures, T₁, a second axis representing the second set of temperatures, T₂, and a third axis representing the third set of temperatures, T₃; and

generating the second equation as an approximation of the three-dimensional plot.

10. The method of claim 9, wherein:

the second equation is T_a=(AT₁+BT₂+CT₃+D)/(A+B+C)

T_a is the ambient temperature; and

A, B, C and D are constants.

11. A system for determining ambient temperature, comprising:

a first temperature sensor situated at a first location in an enclosure;

a second temperature sensor situated at a second location in the enclosure;

a processor connected to the first temperature sensor and the second temperature sensor; and

wherein the processor determines an indication of ambient temperature of a volume proximate to the enclosure based on a two-dimensional relationship representing outputs from the first temperature sensor and the second temperature sensor.

12. The system of claim 11, wherein:

the processor generates an equation approximating the two-dimensional relationship; and

the processor determines the ambient temperature from the equation.

13. The system of claim 12, wherein:

the equation is T_a=(T₁−

AT₂−

B)/(1−

A);

T_a is the ambient temperature;

T₁ is an output of the first temperature sensor;

T₂ is an output of the second temperature sensor; and

A and B are constants.

14. The system of claim 12, further comprising:

a power sensor for determining power levels to an apparatus in the enclosure and connected to the processor; and

wherein the sensor outputs are represented as;

a plot of first temperatures from the first temperature sensor versus power levels from the power sensor;

a plot of the second temperatures from the second temperature sensor versus the power levels from the power sensor;

the plot of the first temperatures versus the power levels is combined with the plot of the second temperatures versus the power levels to result in the plot of the first temperatures versus the second temperatures; and

the plot of the first temperatures versus the second temperatures is the two-dimensional relationship.

15. A system for determining ambient temperature comprising:

a first temperature sensor situated at a first location in an enclosure;

a second temperature sensor situated at a second location in the enclosure;

a third temperature sensor situated at a third location in the enclosure;

a processor connected to the first temperature sensor, the second temperature sensor and the third temperature sensor; and

wherein the processor determines an ambient temperature of a volume proximate to the enclosure based on a three-dimensional relationship representing outputs from the first temperature sensor, the second temperature sensor and the third temperature sensor.

16. The system of claim 15, wherein:

the processor generates an equation approximating the three-dimensional relationship; and

the processor determines the ambient temperature from the equation.

17. The system of claim 16, wherein:

the equation is T_a=(AT₁+BT₂+CT₃+D)/(A+B+C)

T_a is the ambient temperature;

the output of the first temperature sensor is an indication of a first temperature T₁;

the output of the second temperature sensor is an indication of a second temperature T₂;

the output of the third temperature sensor is an indication of a third temperature T₃; and

A, B, C and D are constants.

18. The system of claim 15, wherein:

the output of the first temperature sensor is an indication of a first temperature T₁;

the output of the second temperature sensor is an indication of a second temperature T₂;

the output of the third temperature sensor is an indication of a third temperature T₃; and

the three dimensional relationship is a three-dimensional plot having a first axis representing T₁, a second axis representing T₂, and a third axis representing T₃.

19. The system of claim 18, wherein:

a first T₁, a first T₂ and a first T₃ determined at a first air flow and a first power input to an apparatus situated in the enclosure, are a first coordinate point T₁′

, T₂′

, T₃′

in the three-dimensional plot;

a second T₁, a second T₂ and a second T₃ determined at the first air flow and a second power input to the apparatus, are a second coordinate point T₁″

, T₂″

, T₃″

in the three-dimensional plot;

a third T₁, a third T₂ and a third T₃ determined at a second air flow and the first power input to the apparatus, are a third coordinate point T₁′

″

, T₂′

″

, T₃′

″

in the three-dimensional plot;

the equation (AT₁+BT₂+CT₃+D)/(A+B+C) is an approximation incorporating the first, second and third coordinate points; and

A, B, C and D are constants.

20. The system of claim 19, wherein a fourth T₁, a fourth T₂ and a fourth T₃ determined at a second air flow and the second power input to the apparatus are plotted as a fourth coordinate point T₁″

″

, T₂″

″

, T₃″

″

in the three-dimensional plot.

21. The system of claim 20, further comprising:

determining T₁, T₂, T₃, T₄, and other temperatures (T_N) at additional sets of air flows and power inputs; and

where the temperatures, air flows and power inputs are determined from empirical tests, simulation, calculations and/or modeling.