MOBILE TEMPERATURE SENSOR

• US 20080159354A1
• Filed: 08/09/2007
• Published: 07/03/2008
• Est. Priority Date: 08/09/2006
• Status: Active Grant

• Current Assignee: Spectrasensors, Inc. (Endress+Hauser AG)
• Original Assignee: Spectrasensors, Inc. (Endress+Hauser AG)
• Inventors: Woodward, W. Stephen, Fleming, Rex J., May, Randy Dean
• Granted Patent: US 8,182,143 B2
• Time in Patent Office: Days
• US Class Current: 374/138
• CPC Class Codes: G01K 13/02 for measuring temperature of moving fluids or granular materials capable of flow
• CPC Class Codes: G01K 13/028 for use in total air temperature [TAT] probes

Abstract

Ambient temperature for a temperature sensor can be calculated using a mobile temperature sensor system that samples air from the boundary layer around a mobile platform and passes the air through a measurement cell containing two flush-mounted or embedded sensor elements. A common reference voltage can be applied by control circuitry to minimize drift in the sensor element readings and to calculate the ambient temperature.

Claims

1. An apparatus comprising:

an air intake passage comprising an air intake inlet configured to admit ambient air into the air intake passage;

a measurement cell through which air from within the air intake passage is diverted;

a first sensor element disposed within the measurement cell, the first sensor element providing a signal that is related to a first temperature measured by the first sensor element;

a second sensor element disposed within the measurement cell, the second sensor element providing a signal that is related to a second temperature measured by the second sensor element; and

a control circuit configured to receive the first signal and the second signal and to calculate an ambient air temperature of the ambient air admitted into the air intake passage.

2. An apparatus as in claim 1, further comprising a mobile platform having an exterior surface adjacent to which the air intake inlet is disposed.

3. An apparatus as in claim 2, wherein the mobile platform is an aircraft.

4. An apparatus as in claim 2, further comprising a thermally insulating layer disposed around the measurement cell to thermally isolate the measurement cell from the mobile platform.

5. An apparatus as in claim 2, wherein the air intake inlet is positioned to admit air from within a boundary layer adjacent to the exterior surface of the mobile platform when the mobile platform is in motion.

6. An apparatus as in claim 1, wherein the first sensor element and the second sensor element are platinum resistance thermometers.

7. An apparatus as in claim 1, wherein the measurement cell is constructed of aluminum.

8. An apparatus as in claim 1, wherein the control circuit comprises:

a first biasing and conditioning unit that conditions and biases the first signal;

a second biasing and conditioning unit that conditions and biases the second signal; and

a reference voltage source that normalizes the voltages of the first and the second biasing and conditioning units.

9. An apparatus as in claim 1, further comprising an air sampling vent configured to divert air from within the air intake passage to the measurement cell.

10. An apparatus as in claim 1, wherein the air intake inlet is positioned proximate to an exterior surface of a mobile platform such that ambient air from within a boundary layer of air adjacent to the exterior surface passes into the air intake passage.

11. An apparatus as in claim 1, wherein the air intake inlet is positioned proximate to an exterior surface of a mobile platform such that ambient air from within a boundary layer of air adjacent to the exterior surface passes into the air intake passage.

12. An apparatus as in claim 1, wherein the air intake passage comprises a flow enhancer configured to inertially separate particles and other airborne material with a higher density than the ambient air from air diverted into the measurement cell.

13. An apparatus as in claim 1, wherein the first sensor element is disposed at a first location along an interior surface of the measurement cell and the second sensor element is disposed at a second location along the interior surface of the measurement cell, the first location being approximately opposite to the second location across an interior volume of the measurement cell.

14. An apparatus as in claim 13, wherein the first sensor element is recessed beneath the internal surface and the second sensor is recessed beneath the internal surface.

15. An apparatus as in claim 13, wherein the first sensor element is recessed beneath the internal surface and the second sensor is recessed beneath the internal surface, each by a distance that is in a range of approximately 5 to 100 microns.

16. An apparatus as in claim 13, wherein the first sensor element is recessed beneath the internal surface and the second sensor is recessed beneath the internal surface, each by a distance of approximately 80 microns.

17. A method comprising:

passing ambient air from a boundary layer around a mobile platform into an air intake passage;

diverting a sample stream of air from the air intake passage to a measurement cell, the measurement cell comprising a first sensor element and a second sensor element that provide a first and a second signal related to a measurement cell temperature experienced by the first and the second sensor elements, respectively;

receiving the signals from the first and the second sensor elements at a circuit; and

calculating an ambient temperature of the ambient air using the signals from the two sensor elements.

18. A method as in claim 17, further comprising thermally insulating the measurement cell from the mobile platform.

19. A method as in claim 17, wherein the calculating further comprises applying a common voltage reference to a biasing and conditioning step for each of the first and the second signals.

20. A method as in claim 17, further comprising inertially separating particles and other airborne material with a higher density than the ambient air from air diverted into the measurement cell.

21. A method as in claim 17, wherein the mobile platform is an aircraft.

22. A method as in claim 17, wherein the first sensor element and the second sensor element are platinum resistance thermometers.

23. A method as in claim 17, wherein the first sensor element is disposed at a first location along an interior surface of the measurement cell and the second sensor element is disposed at a second location along the interior surface of the measurement cell, the first location being approximately opposite to the second location across an interior volume of the measurement cell.