| 摘要 |
PURPOSE:To enable measurement of very small distance without any air pressure equipment, by arranging a sound tube having a measuring end at the position separated at a very small distance from the surface of an object to be measured, an acoustic resonance system containing the tube and a sound source for driving the system. CONSTITUTION:A measuring end 2 of an acoustic tube 1 is placed at the position separated from an object 3 to be measured at a small distance through a gap (d) and the measurement of the distance given by the gap (d) utilizes that the sound impedance at the measuring end 2 varies sensitively with the distance. By an acoustic resonance system containing the acoustic tube 1, changes in the impedance are converted into a resonance frequency thereof and changes in the sound pressure therein to detect a very small distance. So to speak, a relatively large sound source 4 of the output acoustic impedance is driven by a sinusoidal wave voltage from an oscillator 5 and the sound pressure returned via the gap (d) is received with a microphone 6 and amplified 7. Then, the sinusoidal wave voltage is converted to DC output E with a rectifying/smoothing circuit 8 to be shown on a display meter 9 and thus, the value of very small distance (d) can be determined. |
