Measuring resonance parameters of piezoelectric transducers
Piezoelectric sensor controllers may facilitate detection and identification of various potential fault states with novel parameter measurements. In an illustrative embodiment of a piezoelectric-based sensor having a shorted-reverberation based resonant frequency measurement, the sensor includes a piezoelectric transducer that provides residual reverberation after being driven. The sensor further includes a controller that provides a low impedance path for the piezoelectric transducer during the residual reverberation and that measures current through the low impedance path to determine a resonant frequency of the piezoelectric transducer. In an illustrative embodiment of a sensing method having a shorted-reverberation based resonant frequency measurement, the method includes: driving a piezoelectric transducer that provides residual reverberation after being driven; providing a low impedance path for the piezoelectric transducer during the residual reverberation; and measuring current through the low impedance path to determine a resonant frequency of the piezoelectric transducer.
1. A piezoelectric-based sensor that comprises:
a piezoelectric transducer that provides residual reverberation after being driven; and
a controller that provides a low impedance path for the piezoelectric transducer during the residual reverberation and measures current through the low impedance path to determine a resonant frequency of the piezoelectric transducer.
2. The sensor of claim 1 , wherein the controller identifies, based at least in part on the resonant frequency, a transducer state from a set of potential states including multiple transducer fault states.
3. The sensor of claim 1 , wherein the controller further determines a quality factor or impedance of the piezoelectric transducer based on the current through the low impedance path.
4. The sensor of claim 3 , wherein the controller identifies, based at least in part on the resonant frequency and on the quality factor or impedance, a transducer state from a set of potential states including multiple transducer fault states.
5. The sensor of claim 4 , wherein the set of potential states includes: normal, loaded, impeded, and defective.
6. A method of operating a piezoelectric-based sensor, the method comprising:
driving a piezoelectric transducer that provides residual reverberation after being driven;
providing a low impedance path for the piezoelectric transducer during the residual reverberation; and
measuring current through the low impedance path to determine a resonant frequency of the piezoelectric transducer.
7. The method of claim 6 , further comprising: identifying, based at least in part on the resonant frequency, a transducer state from a set of potential states including multiple transducer fault states.
8. The method of claim 6 , further comprising: determining a quality factor or impedance of the piezoelectric transducer based on the current through the low impedance path.
9. The method of claim 8 , further comprising: identifying, based at least in part on the resonant frequency and on the quality factor or impedance, a transducer state from a set of potential states including multiple transducer fault states.
10. The method of claim 9 , wherein the set of potential states includes: normal, loaded, impeded, and defective.
11. A piezoelectric-based sensor that comprises:
a piezoelectric transducer that provides residual reverberation after being driven; and
a controller that provides a low impedance path for the piezoelectric transducer during the residual reverberation and measures current through the low impedance path to determine a quality factor Q of the piezoelectric transducer.
12. The sensor of claim 11 , wherein the controller identifies, based at least in part on the quality factor Q, a transducer state from a set of potential states including multiple transducer fault states.
13. The sensor of claim 11 , wherein the controller drives the piezoelectric transducer at a series of different frequencies and measures the low impedance path current as a function of frequency.
14. A piezoelectric-based sensor that comprises:
a piezoelectric transducer; and
a controller that drives the piezoelectric transducer to generate bursts of acoustic energy and, based on a response of the piezoelectric transducer to said driving, derives a quality factor,
wherein the controller measures the quality factor during said driving.
15. The sensor of claim 14 , wherein the controller measures the quality factor by measuring the frequency dependence of the response.
16. A controller for a piezoelectric transducer, the controller comprising:
a transmitter configured to drive a piezoelectric transducer with a carrier signal pulse and to provide a low impedance path during a residual reverberation period after the carrier signal pulse;
a receiver configured to sense a response of the piezoelectric transducer during said residual reverberation by measuring a current through the low impedance path; and
a core logic circuit coupled to the transmitter and to the receiver, the core logic operable to measure a resonant frequency of the piezoelectric transducer based on the response.
17. The controller of claim 16 , wherein the core logic is configured to derive a quality factor Q from the response.
18. The controller of claim 16 , wherein the transmitter is configured to drive the piezoelectric transducer at a series of different frequencies and the receiver measures the low impedance path current as a function of frequency.