| 摘要 |
<p>PURPOSE:To calculate a distance with high precision even when a constant used for distance measurement includes an error by setting the frequency of a plate wave on a vibration transmission plate which is generated by a vibration generating means and the thickness of the vibration transmission plate which propagates the plate wave so that the value of a specific function becomes minimum. CONSTITUTION:To input vibration generated by a vibration source 3, a touch on the vibration transmission plate 8 is made. The plate generated on the vibration transmission plate 8 is detected by a piezoelectric element, etc., fixed on the vibration transmission plate 8 and a vibration sensor 6 which transduces mechanical vibration into an electric signal. The signal from the vibration sensor 6 after being amplified is sent to a signal waveform detecting circuit 9 and processed, and the result is outputted to an arithmetic control circuit 1 to calculates a distance L. The frequency (f) of the plate wave measured as a signal and the thickness (d) of the vibration transmission plate which propagates the plate wave are so set that the value of the function defined as the equation becomes minimum. Here, Vg is a group speed and Vp is a phase speed.</p> |
