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Frequency measuring circuit and resonant pressure sensor type differential pressure/pressure transmitter using the frequency measuring unit

  • US 6,979,995 B2
  • Filed: 09/05/2003
  • Issued: 12/27/2005
  • Est. Priority Date: 10/22/2002
  • Status: Active Grant
First Claim
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1. A frequency measuring circuit comprising:

  • a first counter which counts reference clocks during one cycle of a signal to be measured or a period which is integer times as long as the one cycle, a time difference detection circuit which detects time difference between the signal to be measured and the reference clock, a time expansion circuit which expands an output pulse width of the time difference detection circuit by a given magnification, and a second counter which counts the reference clocks during the pulse width which is expanded by the time expansion circuit, whereinthe frequency of the signal to be measured is obtained based on count values of the first and second counters.

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