| 摘要 |
PURPOSE:To measure an approach distance with high accuracy, by providing a frequency divider which divides the frequency of a reference pulse and receives the control of a frequency dividing ratio by the definite figure-up output of a counter. CONSTITUTION:The transmission pulse transmitted from a transmission circuit 2 is applied to an ultrasonic sensor 1 and an ultrasonic wave is transmitted to an article 9 to be measured while the ultrasonic pulse reflected from the article 9 to be measured is amplified and detected by a receiving circuit 3. When the output of said circuit 3 exceeds reference voltage, an output pulse is generated in an amplitude comparing circuit 4. The transmission pulse of the circuit 2 and the output pulse of the circuit 4 are respectively inputted to a gate circuit 5 to determine the start and stop timings of the gate pulse. The gate pulse generated in the circuit 5 is added to a counter 6 to control the operation of the counter 6. The reference pulse generated from a reference pulse generation circuit 7 receives frequency dividing by a frequency divider 10 to be inputted to the counter 6 and a frequency dividing ratio is controlled by the figure-up output from the counter 6 outputted when the count number of the counter 6 became larger than a preset value.
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