| 摘要 |
PURPOSE:To prevent a malfunction caused by a mutual interference with other ultrasonic detector by measuring and storing a repeated period and a continuation time of a noise having a periodicity, avoiding a periodic noise from this storage data, etc., and executing the transmission and reception. CONSTITUTION:An ultrasonic vibrator 1 used for both transmission and reception is driven by a transmitting circuit 2 and transmits intermittently an ultrasonic pulse, and receives a reflected wave pulse from an object. A receiving signal is amplified by a receiving circuit 3, and also, inputted to an amplifying and detecting circuit 4 and an object detecting circuit 5, and a distance to the object is calculated and displayed on an indicator 6. In that case, an output of the receiving circuit 3 is inputted to a noise detecting circuit 7, and a repeated period and a continuation time of a noise are detected and stored by a storage circuit 9. Subsequently, by a signal processing circuit 8, an output of the noise detecting circuit 7 and storage data from the storage circuit 9 are received, and the transmitting circuit 2 is controlled so that transmission and reception are executed, while avoiding a periodic noise. |
