| 摘要 |
PURPOSE:To accurately detect the deterioration of an ultrasonic vibrator, by judging the abnormal lowering of a current on the basis of information of a current flowing to the ultrasonic vibrator after a predetermined time is elapsed from the point of time when the application of an exciting rectangular wave signal to the ultrasonic vibrator is started. CONSTITUTION:A control circuit 7 for controlling the analogue switch 8 of an exciting current detector 4 responds by an intermittent rectangular wave signal for exciting an ultrasonic vibrator 1 and a current flowing to the vibrator 1 through a resistor 6 after a predetermined time is elapsed from the point of time when the application of the rectangular wave signal is started is detected through an amplifier 9 and an envelope detector 10. When the detected current reaches a predetermind value or less, this state is judged and detected by a comparator 11, a D type FF 12, a pulse generator 13 and a latch 14 and the abnormal lowering of a current is alarmed through the circuit 14. By this mechanism, the deterioration of the ultrasonic vibrator of an obstacle detecting apparatus is accurately detected. |
