ULTRASONIC SENSOR AND ITS OPERATING FREQUENCY SETTING METHOD

摘要

PROBLEM TO BE SOLVED: To provide an ultrasonic sensor enabling operating frequency setting regardless of the liquid state inside a receptacle, either empty or present. SOLUTION: When the inner state of a receptacle 1 is empty and an operating frequency should be set, an operator selects a previously given receptacle number using a receptacle number selection button 10 and then selects an empty state 'E' out of selection buttons for the presence of liquid in a receptacle 9 to press a run button 11. An operating frequency setting circuit 12 allows a variable frequency ultrasonic wave on the basis of the center frequency entered in a receptacle number-based frequency table 13 to be emitted from a probe 4, setting the frequency of minimum attenuation as the operating frequency. A detecting action control circuit 14 stores not only this set operating frequency 15 but also a timing information for receiving an abnormal reflected wave generated at that time 16 so as to unuse any received reflected wave matching with this timing for liquid level detection.