Ultrasonic sensor and pipetting apparatus using same

摘要

An ultrasonic sensor detects the time of rise of the first of transmitted waves and also detects peak points Po appearing in the waveform of received waves to detect a waveform reference point where the time-base coordinate of a phantom envelope connecting these peak points Po is a minimum. The time T2 of rise of the first of the received waves is calculated by adding a predetermined period of offset time To to the time t2 of the waveform reference point of the received waves to calculate the elapsed time DELTA T from the time of rise of the first transmitted wave to the time of rise of the first received wave. The distance L to an object of measurement is calculated based on the result of calculation. The distance L to the object can be calculated alternatively based on the elapsed time DELTA T' from a waveform reference point of the transmitted waves to the waveform reference point of the received waves. The sensor thus realized gives measurements with high accuracy even with use of ultrasonic waves of relatively low frequency. <IMAGE>