Field device with self-testing of a piezoelectric transducer
First Claim
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1. A field device comprising:
- a piezoelectric transducer having a first terminal and a second terminal;
normal mode circuitry for operating the piezoelectric transducer during a normal operation mode; and
self-test circuitry for supplying a charging current to the piezoelectric transducer during a diagnostic self-test mode and providing a test signal as a function of voltage on the piezoelectric transducer as a result of the charging current, wherein the self-test circuitry includes;
a resistor for supplying the charging current through the resistor to the first terminal of the piezoelectric transducer; and
switching circuitry for disconnecting the normal mode circuitry, for connecting the resistor to the first terminal of the piezoelectric transducer, and for connecting the second terminal to ground during the diagnostic self-test mode,wherein, during the diagnostic self-test mode, the self-test circuitry samples the voltage on piezoelectric transducer within a predetermined time period after the charging current is supplied to the piezoelectric transducer,wherein, if the voltage on the piezoelectric transducer exhibits a RC charging curve representative of a normal capacitance indicated by the sampled voltage being between a first threshold value and a second threshold value, then the self-test circuitry provides a test signal that indicates a normal condition.
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Abstract
An industrial process field device having a piezoelectric transducer performs self-testing of the condition of the piezoelectric transducer during a self-test mode. A charging current is supplied to the piezoelectric transducer, and voltage on the piezoelectric transducer as a result of the charging current is monitored. A diagnostic test result indicating condition of the piezoelectric transducer is produced based on the magnitude of the voltage.
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Citations
13 Claims
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1. A field device comprising:
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a piezoelectric transducer having a first terminal and a second terminal; normal mode circuitry for operating the piezoelectric transducer during a normal operation mode; and self-test circuitry for supplying a charging current to the piezoelectric transducer during a diagnostic self-test mode and providing a test signal as a function of voltage on the piezoelectric transducer as a result of the charging current, wherein the self-test circuitry includes; a resistor for supplying the charging current through the resistor to the first terminal of the piezoelectric transducer; and switching circuitry for disconnecting the normal mode circuitry, for connecting the resistor to the first terminal of the piezoelectric transducer, and for connecting the second terminal to ground during the diagnostic self-test mode, wherein, during the diagnostic self-test mode, the self-test circuitry samples the voltage on piezoelectric transducer within a predetermined time period after the charging current is supplied to the piezoelectric transducer, wherein, if the voltage on the piezoelectric transducer exhibits a RC charging curve representative of a normal capacitance indicated by the sampled voltage being between a first threshold value and a second threshold value, then the self-test circuitry provides a test signal that indicates a normal condition. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A method for testing condition of a piezoelectric transducer in a field device, the method comprising:
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disconnecting normal mode circuitry from the piezoelectric transducer during a test period; supplying a charging current through a resistor to a first terminal of the piezoelectric transducer during the test period; connecting a second terminal of the piezoelectric transducer to ground during the test period; monitoring a voltage on the piezoelectric transducer as a result of the charging current during the test period; and producing a diagnostic test result indicative of condition of the piezoelectric transducer based upon magnitude of the voltage, wherein the produced diagnostic test result indicates a normal condition, if the monitored voltage on the piezoelectric transducer exhibits a RC charging curve representative of a normal capacitance indicated by the monitored voltage being between a first threshold value and a second threshold value. - View Dependent Claims (11, 12, 13)
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Specification