Claims
- 1. Apparatus for detecting presence of a sensor, the apparatus comprising:
a signal source for providing an excitation signal for the sensor; a detector circuit for detecting a response signal from the sensor in response to the excitation signal for presence detection; a switch responsive to a control signal for switching between a first switch state coupling the signal source to the sensor and a second switch state coupling the detector circuit to the sensor; and a controller for providing the control signal and for analyzing the detected response signal.
- 2. The apparatus of claim 1 wherein the detector circuit detects the amplitude of the response signal.
- 3. The apparatus of claim 1 wherein the detector circuit includes a charge converter having an input for coupling to the sensor through the switch for the second switch state, the charge converter adapted to amplify the response signal; a peak and hold detector coupled to the output of the charge converter for providing an analog peak response signal; and an analog to digital converter for converting the analog peak response signal to a digital peak response signal for analysis by the controller.
- 4. The apparatus of claim 1 wherein the signal source provides a multi-frequency excitation signal.
- 5. The apparatus of claim 4 wherein the multi-frequency excitation signal has a sweep frequency range from about 5 kHz to about 50 kHz.
- 6. The apparatus of claim 4 wherein the multi-frequency excitation signal has a sweep frequency range which includes a resonant frequency of the sensor.
- 7. The apparatus of claim 1 wherein the controller is programmed to conduct a first test and a second test of the sensor and to determine presence of the sensor from the first and second tests.
- 8. The apparatus of claim 7 wherein the detector circuit includes a variable gain charge converter for amplifying the response signal and wherein the controller is programmed to set the gain to a first level for the first test and to set the gain to a second level for the second test.
- 9. The apparatus of claim 1 wherein the controller controls the signal source.
- 10. A method for detecting presence of a sensor, the method comprising:
coupling a swept frequency excitation signal to a sensor for a time interval; coupling the sensor to a detector circuit following the time interval to detect a response signal from the sensor; and analyzing the amplitude of the detected response signal to determine presence of the sensor.
- 11. The method of claim 10 wherein the method is conducted for a first test and repeated for a second test to determine presence of the sensor from the first and second tests.
- 12. A method for detecting presence of a sensor, the method comprising:
coupling an excitation signal to a sensor for a first time interval; coupling the sensor to a charge converter following the first time interval to receive a response signal from the sensor; charging a peak and hold detector with the response signal for a second time interval to provide a response amplitude signal; and analyzing the response amplitude signal to determine presence of the sensor.
- 13. The method of claim 12 wherein the method is conducted for a first test and repeated for a second test to determine presence of the sensor from the first and second tests.
- 14. The method of claim 13 wherein coupling the sensor to the charge converter includes setting the gain of the charge converter to a first level for the first test and setting the gain to a second level for the second test.
- 15. The method of claim 12 wherein the excitation signal is a multi-frequency excitation signal.
- 16. The method of claim 15 wherein the multi-frequency excitation signal has a sweep frequency range from about 5 kHz to about 50 kHz.
- 17. The method of claim 16 wherein the multi-frequency excitation signal has a sweep frequency range which includes a resonant frequency of the sensor.
RELATED APPLICATION
[0001] This application claims the benefit of U.S. Provisional Application No. 60/184,674, filed on Feb. 24, 2000, the entire teachings of which are incorporated herein by reference.
Provisional Applications (1)
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Number |
Date |
Country |
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60184674 |
Feb 2000 |
US |