| 摘要 |
<p>PURPOSE:To surely make a judgement as to whether or not there is some abnormality in an ultrasonic vibrator by comparing the period of time required for the level of a signal sampled from an ultrasonic-wave transmitting portion to fall from first to second threshold value to a predetermined period of time. CONSTITUTION:A first comparing portion 10 compares the level of a signal sampled from a wave transmitting portion 2 with a first threshold value and a second comparing portion 11 compares the level of the signal with a second threshold value and the result of each comparison is input to a control portion 7. Next, a period detecting portion 72 detects the period of time required for the signal level being less than the first threshold value to fall to below the second threshold value. A period comparing portion 73 judges when the detected period of time is longer than a predetermined period of time that there is no abnormality and otherwise the portion 73 judges that there is some abnormality. The first and second threshold values are properly set so as to surely detect whether or not there is some abnormality in an ultrasonic vibrator 1 such as adhesion of foreign material to the vibration face of the vibrator 1, etc.</p> |
