| 摘要 |
PURPOSE: To stably and accurately detect the presence or absence of liquid and the liquid level position without being affected by the peak level of a reflection wave and noise by providing a sensor head and comparison, measurement, and judgment circuits. CONSTITUTION: Ultrasonic waves transmitted horizontally from sensor heads 2a and 2b return as reflection waves from the opposing inner surfaces of a liquid bath and are received as by sensor heads 2a and 2b. The received waves are inputted to a comparison circuit 6, a part exceeding a certain reference voltage is binary-coded and detected by a circuit 6, and the life time is measured by a measuring circuit 7. Then, the life time of the measured binary-coded signal is compared with a preset reference time by a judgment circuit 8 to judge the presence or absence of a liquid W. By taking out a life time exceeding a certain level (reference voltage) of the reception signal and comparing it with a reference time, the value of a peak level does not matter and the influence of a sporadic and narrow noise can be excluded, thus achieving a positive and stable judgment. |
