| 摘要 |
PURPOSE:To prevent a detected distance from being varied due to a temperature variation, by stopping the sampling, when a noise component is superposed on a receiving signal, and fetching exactly a temperature signal. CONSTITUTION:A temperature of a sensor part 2 is detected by a temperature detecting circuit 8. An output from an ultrasonic vibrator 5 and an output of the temperature detecting circuit 8 are added by an adder 7, and sent out to an amplifying unit 1 through a detecting circuit 9. A sample holding circuit 24 of the amplifying unit 1 samples only a temperature signal from an output of the detecting circuit 9. This sample holding circuit 24 is brought to a non- operation, when a noise is detected by a comparing circuit 23. From a detecting gate generating circuit 26, a gate signal of pulse width corresponding to a temperature is outputted, and applied to a signal processing circuit 28. By the signal processing circuit 28, an object within a prescribed range is detected.
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