| 摘要 |
The present invention provides a barometer which includes a frequency control circuit connected to the input of the piezoelectric oscillator, a current-voltage converter connected to the output of the piezoelectric oscillator, a phase comparator connected to the output of the frequency control circuit and to the output of the current-voltage converter, a voltmeter connected to the current-voltage converter, a voltmeter connected to the phase comparator, a low-pass filter connected to the phase comparator, and input means for applying the output of the low-pass filter to the frequency control circuit. In the construction described above, the ambient pressure of the gas around the piezoelectric oscillator is represented by the a.c. voltage value of the piezoelectric oscillator.
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