| 摘要 |
PURPOSE:To prevent a wrong judgment from being committed owing to a multiple reflected wave by providing gate means that is opened and closed by a falling from binary-coding means based on a driving pulse given to a ultrasonic oscillator and measuring means for measuring the rising of a binary-coded signal. CONSTITUTION:An ultrasonic oscillator 3 is supplied with a driving pulse from a driving circuit 2. A received signal processing circuit 4 binary-codes a received signal from the oscillator 3 at a given threshold value. A gate circuit 5 passes a binary-coded signal under a given condition and inputs the signal to a CPU 1. The CPU 1 controls opening and closing the circuit 5 on the basis of the binary-coded signal from the circuit 4. In such a constitution, counters 11 and 12 begin their measurements at the rising of a driving signal. The CPU 1 detects the falling of the received binary-coded signal to open the circuit 5. Then, the CPU 1 judges whether the received signal from the circuit 5 is present and whether a transmitted signal agrees with the received signal. Further, the CPU 1 judges whether the received binary-coded signal from the circuit 5 is within a measuring section and, when the received binary-coded signal is within the section, performs a processing within the measuring section. |
