Wireless Telemetry Circuit Structure for Measuring Temperature in High Temperature Environments

• US 20100039288A1
• Filed: 08/15/2008
• Published: 02/18/2010
• Est. Priority Date: 08/15/2008
• Status: Active Grant

• Current Assignee: Wolfspeed, Inc.
• Original Assignee: Siemens Power Generation, Inc., Arkansas Power Electronics International, Inc. (Wolfspeed, Inc.)
• Inventors: FRALEY, JOHN R., ROESCH, EDWARD R., LOSTETTER, ALEXANDER B., MITCHELL, DAVID J., SCHUPBACH, ROBERTO, WESTERN, BRYON, WAITS, ROD, SUBRAMANIAN, RAMESH, KULKARNI, ANAND A., MCPHERSON, BRICE
• Granted Patent: US 8,092,080 B2
• Time in Patent Office: Days
• US Class Current: 340/870.20
• CPC Class Codes: G01K 1/024 for remote indication
• CPC Class Codes: G01K 1/026 arrangements for monitoring a plurality of temperatures, e.g. by multiplexing
• CPC Class Codes: G01K 13/08 in rotary movement
• CPC Class Codes: G01K 7/021 Particular circuit arrangements G01K7/026, G01K7/12, G01K7/14 take precedence
• CPC Class Codes: G01K 7/13 Circuits for cold-junction compensation
• CPC Class Codes: G01K 7/34 using capacitative elements capacitors per se H01G
• CPC Class Codes: H04Q 2209/40 using a wireless architecture
• CPC Class Codes: H04Q 9/00 Arrangements in telecontrol or telemetry systems for selectively calling a substation from a main station, in which substation desired apparatus is selected for applying a control signal thereto or for obtaining measured values therefrom

Abstract

A circuit affixed to a moving part of an engine for sensing and processing the temperature of the part. The circuit generates a signal representative of the temperature sensed by a thermocouple (110) and amplified by an amplifier (112). A square wave oscillator (113) with a temperature sensitive capacitor (C8) varies its frequency in response to changes of a local temperature of the circuit. A chopper (114, J27) converts the output of the amplifier into an alternating current signal. The chopper is gated by the square wave oscillator and a second input is coupled to an output of the amplifier. Thus, the chopper has an output signal having a frequency representative of the local temperature and an amplitude representative of the thermocouple temperature, whereby the combined signals represent the true temperature of the part.

Claims

1. In a telemetry system for use in an internal combustion engine, a circuit structure affixed to a moving part of said engine and being disposed for processing information sensed about the temperature of said moving part, said circuit structure being adapted for the high temperature environment of said engine and comprising:

a thermocouple disposed on said moving part for sensing a temperature thereof and providing a signal representative of the temperature sensed;

an amplifier having an input coupled to an output of said thermocouple and being disposed for amplifying the signal representative of the temperature sensed by said thermocouple;

a square wave oscillator disposed for generating a square wave signal having a frequency indicative of a local temperature of said circuit structure;

a chopper disposed for converting an output signal of said amplifier into an alternating current signal, said chopper having a first gating input coupled to an output of said square wave oscillator and a second input coupled to an output of said amplifier, said chopper having an output providing a signal having a frequency representative of the local temperature of said circuit and an amplitude representative of the temperature sensed by said thermocouple.

2. The system as in claim 1 wherein said square wave oscillator includes a feedback coupling capacitor having a capacitance variable with temperature, whereby an increase in the local temperature of said circuit structure causes a decrease in capacitance of said coupling capacitor thereby causing a predictable increase in the frequency of said output signal of the square wave oscillator.

3. The system as in claim 1 wherein said square wave oscillator includes a differential amplifier having an RC feedback network coupled between the input and the output of said amplifier and having a capacitor coupled between said RC feedback network and said output of said amplifier, wherein said capacitor has a temperature sensitive dielectric so that a capacitance thereof changes proportionally in response to changes in temperature, thereby changing the frequency of said square wave signal in response to changes in temperature.

4. The system as in claim 3 wherein the dielectric of said capacitor is classified as X7R.

5. The system as in claim 1 further comprising structure for transmitting said sensed information to a receiver external to said engine comprising a voltage controlled oscillator having an input disposed for receiving said alternating current signal from said chopper and for producing a radio frequency signal representative of the temperature sensed by said thermocouple, said radio frequency signal being coupled to an antenna for transmission to a receiver remote from said engine.

6. The system as in claim 5 further comprising a buffer coupled between said voltage controlled oscillator and said antenna for buffering said radio frequency signal.

7. The system as in claim 5 wherein said voltage controlled oscillator comprises a Colpitts oscillator for setting a reference carrier frequency.

8. The system as in claim 7 wherein said Colpitts oscillator comprises an inductance coil in parallel with a pair of serially coupled capacitors at a circuit node.

9. The system as in claim 8 wherein said inductance coil comprises a coil of wire formed directly on a printed circuit board supporting said circuit.

10. The system as in claim 7 wherein said Colpitts oscillator comprises a gallium nitride (GaN) LED diode coupled in a reverse bias configuration as a varactor and in parallel with one of said capacitors between said circuit node and ground potential.

11. The system as in claim 10 wherein said LED diode comprises indium gallium nitride (InGaN).

12. The system as in claim 1, further comprising an ac power conditioning circuit for providing dc power to the circuit structure, said ac power conditioning circuit including an array of rectifying diodes, filtering capacitors, and temperature compensating voltage regulators, each comprising:

a first transistor coupled in parallel with said filtering capacitors and having a source terminal coupled to ground potential through a pair of resistors and having a gate terminal coupled to the junction between said pair of resistors, a first of said pair of resistors having a zero coefficient of resistance coupled between said source terminal and the junction and a second of said pair of resistors having a positive coefficient of resistance coupled between the junction and ground potential, whereby said first transistor and pair of resistors act as a constant current source;

a second transistor coupled in series with the positive output of said ac power conditioning circuit and having a gate terminal coupled to the junction between said pair of resistors, whereby the bias voltage on said gate terminal of said second transistor shifts as a function of temperature changes, thereby making the voltage drop across said second transistor constant over a range of temperature changes.

13. The system as in claim 12 wherein in said ac power conditioning circuit said first of said pair of resistors comprises tantalum nitride.

14. The system as in claim 12 wherein in said ac power conditioning circuit said second of said pair of resistors comprises platinum.

15. The system as in claim 12 wherein in said as power conditioning circuit said first of said pair of resistors has a negative coefficient of resistance and comprises silicon carbide.

16. The system as in claim 12 wherein in said as power conditioning circuit said second of said pair of resistors has a zero coefficient of resistance and comprises tantalum nitride.

17. In a telemetry system for use in an internal combustion engine, a circuit structure affixed to a moving part of said engine and being disposed for processing information sensed about a temperature of said moving part and for transmitting said sensed information to a receiver external to said engine, said circuit structure being adapted for the high temperature environment of said engine and comprising:

a thermocouple disposed on said moving part for sensing the temperature thereof and providing a signal representative of the temperature sensed;

an amplifier having an input coupled to an output of said thermocouple and being disposed for amplifying the signal representative of the temperature sensed by said thermocouple;

a square wave oscillator disposed for generating a square wave signal having a frequency indicative of a local temperature of said circuit structure and including a feedback coupling capacitor having a capacitance variable with temperature, whereby an increase in the temperature of said circuit structure causes a decrease in capacitance of said coupling capacitor thereby causing a predictable increase in the frequency of said square wave signal;

a chopper disposed for converting an output signal of said amplifier into an alternating current signal, said chopper having a first gating input coupled to an output of said square wave oscillator and a second input coupled to the output of said amplifier, said chopper having an output providing a signal having a frequency representative of the local temperature of said circuit structure and an amplitude representative of the temperature sensed by said thermocouple; and

,

a voltage controlled oscillator having an input disposed for receiving said alternating current signal from said chopper and for producing a radio frequency signal representative of the temperature sensed by the thermocouple, said radio frequency signal being coupled to an antenna for transmission to a receiver remote from said engine.

18. The system as in claim 17 wherein said square wave oscillator comprises a differential amplifier having an RC feedback network coupled between an input and an output of said amplifier and having a capacitor coupled between said RC feedback network and said output of said amplifier, wherein said capacitor has a temperature sensitive dielectric so that the capacitance thereof changes proportionally in response to changes in temperature, thereby changing the frequency of said square wave signal in response to changes in temperature.

19. The system as in claim 18 wherein the dielectric of said capacitor is classified as X7R.

20. The system as in claim 17 wherein said voltage controlled oscillator comprises a Colpitts oscillator for setting a reference carrier frequency, said oscillator comprises an inductance coil in parallel with a pair of serially coupled capacitors at a circuit node and comprising a coil of wire formed directly on a printed circuit board supporting said circuit.

21. The system as in claim 20 wherein said Colpitts oscillator comprises a gallium nitride (GaN) LED diode coupled in a reverse bias configuration as a varactor and in parallel with one of said capacitors between said circuit node and ground potential.