| 摘要 |
PURPOSE:To display stable performance which hardly causes an error in measurement, by detecting the oscillation frequency variation of an oscillator consisting of one side of a voltage vibrator and an amplifier by the resonance characteristic of the other side of the voltage vibrator. CONSTITUTION:A liquid level switch has the 1st piezoelectric vibrator 10 and the 2nd piezoelectric vibrator 12 which have mutually uniform characteristics, and the vibrating surface 14 of the 1st piezoelectric vibrator 10 is positioned where detection is performed; the oscillator 18 consists of the 1st piezoelectric vibrator 10 and the 1st amplifier 16, the oscillation output of the oscillator 18 is supplied to the 2nd vibrator 12, and the resonance output of the 2nd vibrator 12 is regarded as a detection output. Then, the oscillation frequency variation of the oscillator 18 is detected by the resonance characteristic of the 2nd piezoelectric vibrator 12 to display the stable performance which hardly causes an error in measurement. |
