| 摘要 |
<p>PURPOSE:To improve the temperature characteristic of a sensor, to make the pressure sensitivity approximately uniform even when a bending part is present and to eliminate influences of the stain by receiving sound waves or ultrasonic waves propagating inside a tubular elastic body. CONSTITUTION:A transmitter 3 converts an oscillating signal VT supplied from an oscillator 5 to a sound wave or ultrasonic wave SO and feeds the same into a tubular elastic body 2. The sound wave SO propagates in the tubular elastic body 2 to reach a receiver 4. The receiver 4 converts the sound wave SO to an electric signal VR which passes through an amplifier 6 to be a signal VA. The signal VA is supplied to a total wave rectifying/smoothing circuit 7 and converted and output as an output voltage VOUT. The absorbing rate of the sound waves or ultrasonic waves by the air inside the tubular elastic body 2 is hardly changed to the temperature of the air. Therefore, a sensor 1 has good temperature characteristic. When the tubular elastic body 2 is pressed by the outside pressure, the propagating passage of the sound wave SO at a part of the pressed tubular elastic body 2 becomes narrow, and therefore the level of the voltage VOUT output from 7 is lowered. Accordingly, it is possible to detect whether a foreign obstacle is inserted by detecting the voltage VOUT.</p> |
