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Field device with self-testing of a piezoelectric transducer

  • US 9,310,412 B2
  • Filed: 05/28/2012
  • Issued: 04/12/2016
  • Est. Priority Date: 01/20/2012
  • Status: Active Grant
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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