JPS5786043A - Sludge searcher - Google Patents

Abstract

PURPOSE:To eliminate measurement errors owing to a difference in rise times by deviating the transmission timing of both ultrasonic wave signals by the time corresponding to the difference in the rise time of received output waveforms. CONSTITUTION:First, ultrasonic signals S3, S4 of high and low frequencies from transmitters and receivers 8, 9 are reflected by an artificial reflection body 25 and are received in the transmitters and receivers 8, 9. The difference (t) in the times counted by depth counting circuits 13, 14 in a subtraction circuit 24 is transmitted to a delay circuit 23, and the (t) is subtracted from a set time T, by which a delay time is set. Next, the body 26 is removed. When a transmission timing pulse is generated in a circuit 22, it is delayed by T-t by the circuit 23 and is transmitted via a circuit 25 to a pulse generating circuit 3, from which the pulse-like signal of a low frequency is generated and the ultrasonic signal S2' of the low frequency is emitted from the transmitter and receiver 9 through an amplifier 5 and a transmission-reception selector 7 toward a sludge layer 20. The ultrasonic signal S1 of a high frequency is emitted from the transmitter and receiver 8 by the similar operation, and depths D1, D2 are calculated by the circuits 13, 14.