| 摘要 |
PURPOSE:To use an ultrasonic oscillator itself as a detecting element and to perform temperature compensation without providing any special parts such as a thermistor by detecting variation in the electrostatic capacity of the ultra sonic oscillator and driving a temperature compensating circuit. CONSTITUTION:The ultrasonic oscillator 2 for both transmission and reception which is made of, for example, titanate dielectric ceramic is connected to the common terminal (c) of a switch 9 and a detection gate 4 and an automatic transmission/reception changeover circuit 1 are connected to contacts (a) and (b). Then, the electrostatic capacity of the oscillator 2 increases proportional to a temperature rise, so the variation in the electrostatic capacity is detected by the gate 4 by switching the switch 9 to the side of the contact (a) automati cally from the completion of reception to right before the start of transmission and the oscillation frequency of an oscillation circuit 5 is varied by the gate 4 after the voltage-controlled oscillator in the gate 4 is operated, thereby performing the temperature compensation corresponding to the ambient tempera ture. |
