Frequency measuring circuit and resonant pressure sensor type differential pressure/pressure transmitter using the frequency measuring unit
First Claim
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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Abstract
A time difference signal having a pulse width corresponding to the time difference between an output of a resonant pressure sensor and a reference clock is prepared. The pulse width of the time difference signal is expanded by a given magnification. Based on a count value obtained by counting the reference clock during the expanded pulse width and a count value obtained by counting the reference clock during one cycle of the output of the resonant pressure sensor or a period which is integer times as long as the one cycle, the output frequency of the resonant pressure sensor is obtained. It is possible to obtain the fast processing and the high resolution without increasing the frequency of the reference clock.
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Citations
14 Claims
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1. A frequency measuring circuit comprising:
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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, wherein the frequency of the signal to be measured is obtained based on count values of the first and second counters. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A resonant pressure sensor type differential pressure/pressure transmitter comprising:
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a first counter which counts reference clocks during one cycle of a resonant pressure sensor 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 difference expansion circuit, wherein the frequency of the signal to be measured is obtained based on count values of the first and second counters, and pressure is obtained based on the frequency. - View Dependent Claims (9, 10, 11, 12, 13, 14)
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Specification