| 摘要 |
PURPOSE:To accurately measure concentration or pressure even when external vibration is intense by providing an LPF, an HPF, etc. CONSTITUTION:The oscillation circuit 13 which consists of the LPF 5, the HPF 12, an amplifying circuit 9, and a vibration system 8 is powered on to apply a driving signal 4 to the vibration system 8. At this time, signal components of frequencies F1-Fn appear in a displacement signal 6, but the signal components of frequencies F2-Fn are attenuated by the LPF 5 more than the signal component of frequency F1. If a converter is applied with external vibration when the vibration system 8 vibrates, a component of the external vibration appear in the signal 6, but the component is attenuated by the HPF 12 when it is lower than a cut-off frequency. The input signal component of frequency F1 appears at the circuit 9 and is 90 deg. delayed behind the signal 6 and the phase of the signal component of frequency F1 is 180 deg. delayed behind the signal 4 on the input side of the circuit 9, so the circuit 13 continues to vibrate at the frequency F1. Consequently, the concentration or pressure of the fluid 7 is measured with the output signal 11a of a pulsating circuit 11.
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