| 摘要 |
PURPOSE: To suppress the disturbance signal generated in the case of operating an ultrasonic proximity initiator by deciding one stepwise function as a role of disturbance noise threshold value with a reception signal as a foundation. CONSTITUTION: An ultrasonic initiator 1 repeatedly sends an ultrasonic pulse, and then generates an analog reception signal having an accessory use echo signal at the output terminal of the initiator 1. The reception signals are evaluated in a control and evacuating unit 2. First, one stepwise function 11 serving as a role of disturbance noise threshold value is decided with the reception signal as a foundation, and then the timing creation of the use echo signal is obtained by comparing the function 11 with the signal. Then, the echo propagating time of the use echo signal starting from the start of sending is obtained, and the propagating time is transmitted to the unit 2. Thus, the function 11 can be suppress the noise by considering the lapse of time as the threshold value relative to the time.
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