| 摘要 |
PURPOSE:To enable to measure accurately blocks existing in places being off the moving direction, by receiving oscillated pulses with a plurality of receivers and detecting a time difference between said pulses and the pulses first received among them. CONSTITUTION:A plurality of ultrasonic wave pulse oscillators 13a, 13b and pulse receivers 21a, 21b are provided, and a time difference between received time of a reflected pulse received first and oscillated time of the pulse is detected using a detecting circuit 3 and indicated on an indicator 4. For example, ultrasonic wave pulses are oscillated from an oscillating unit 1, and said pulses are received with a plurality of pulse receivers 21a, 21b, rectified and shaped. Further, the pulses received first among them are selected by use of an OR gate 7. And, a time defference is detected by a reference clock signal from a signal generator and output signals of a flip-flop 3 that is set at the leading edge of the oscillated pulse and is reset at the leading edge of the received pulse. |
