Transducer in-situ testing apparatus and method
The present invention is directed to an apparatus and method for a measurement system for the testing of transducers, and more particularly to the testing of piezoelectric transducers. The measurement system includes a transducer, a feedback amplifier coupled to the transducer and a signal processing circuit coupled to the output of the amplifier. The method of testing the transducer includes coupling the test signal to the transducer, disabling the amplifier, and measuring the response of the transducer to the test signal with the test processing circuit. The circuit itself used for performing this method includes a piezoelectric transducer, an amplifier, including a feed-back circuit coupled to the amplifier for amplifying the output of the transducer, a power source coupled to the amplifier, a signal source generating a test signal having a frequency spectrum at least overlapping the self resonant frequency of the transducer coupled to the transducer, and a switch coupled to the amplifier capable of disabling the amplifier.
1. In a measurement system comprising a transducer, a charge amplifier having a feedback element, coupled to the transducer and a signal processing circuit coupled to an output of the amplifier, a method of testing the transducer in-situ comprising:
a. coupling a test signal to the transducer;
b. disabling the amplifier while leaving the feedback element in place; and
c. analyzing the response of the transducer to the test signal with the signal processing circuit.
2. The method of claim 1 further comprising coupling an analyzer to an output of the amplifier and measuring the response of the transducer.
3. The method of claim 1 comprising coupling the test signal to the amplifier through an impedance.
4. The method of claim 3 in which the impedance comprises a capacitor.
5. The method of claim 1 further comprising coupling the test signal to a resistor and on to an output of the amplifier.
6. The method of claim 1 further comprising comparing a measured response of the transducer to a signature response.
7. The method of claim 6 wherein the signature response comprises a measured response of an unmounted transducer.
8. The method of claim 6 wherein the signature response comprises a measured response of a mounted transducer to a test signal prior to initiating operations with the transducer.
9. The method of claim 8 wherein the measured response is characterized by one or more specific amplitudes and/or frequencies.
10. The method of claim 9 further comprising generating an error signal when the amplitude and/or frequency of the measured response falls outside a predetermined range.
11. The method of claim 6 wherein the signature response further comprises a measured response of a transducer during normal operation.
12. The method of claim 1 further comprising coupling the test signal to an output of the amplifier at a connection to the amplifier feedback component.
13. The method of claim 1 further comprising coupling the test signal between an output of the transducer and an input to the amplifier.
14. The method of claim 1 in which the test signal has an amplitude approximating the maximum allowed.
15. The method of claim 1 in which the measured response is normalized for various conditions comprising environmental conditions.
16. In a measurement system comprising a transducer, an amplifier comprising a feedback element, coupled to the transducer and a signal processing circuit coupled to an input of the amplifier, a method of testing the transducer in-situ comprising:
a. coupling a test signal to the transducer;
b. disabling the amplifier while leaving the feedback element in place; and
c. analyzing the response of the transducer to the test signal with the signal processing circuit.
17. In a measurement system comprising a transducer, an amplifier having a feedback element coupled to the transducer and a signal processing circuit coupled to an output of the amplifier, a method of testing the transducer in-situ comprising:
a. coupling a test signal to the transducer;
b. disabling the amplifier while leaving the feedback element in place;
c. analyzing the response of the transducer to the test signal with the signal processing circuit; and
d. comparing a measured response of the transducer to a signature response wherein the signature response comprises a measured response of an unmounted transducer.
18. The method of claim 17 wherein the measured response of the transducer with built-in test whose output is programmed to assume a predetermined value when an unacceptable fault condition is detected.
19. The method of claim 17 wherein the measured response of the transducer with built-in test whose output is modulated with a signal reflecting the results of a detected fault condition.
20. The method of claim 17 wherein the measured response of the transducer with built-in test that provides an additional interface for communication of test results.
21. The method of claim 17 wherein the measured response of the transducer with built-in test that uses the results of the test to appropriately compensate its analog output signal.