JPS5796255A - Sludge detector - Google Patents

Abstract

PURPOSE:To enable easy reading of the thickness of a sludge layer by recording the depth of the surface of sludge and that of the layer of the bottom of the water separately on recording paper without changing the scanning speed of a recording pen. CONSTITUTION:An ultrasonic signal S1 having high frequency and an ultrasonic signal S2 having low frequency are transmitted toward a sludge layer 17 in the water and the recording pen 14 is made to operate at the time of respective reception of the high- frequency ultrasonic signal reflected at the surface 17a of sludge and of the low- frequency ultrasonic signal reflected at the surface 18 of the bottom of the water, whereby the depth of the surface of sludge and of the surface of the bottom of the water is recorded on the recording paper 15. Oscillators 25 and 32 oscillate clock-pulses having frequencies f1 and f2 (f1>f2) respectively, while counting circuits 26 and 27 count the clock-pulse of the frequency f1 in the period between the points of time of transmission and reception of both ultrasonic signals S1 and S2, respectively. Meanwhile, a counting circuit 33 counts the clock-pulse of the frequency f2. Coincidence circuits 28 and 29 compare the contents of the counting circuits 26 and 27 with that of 33, and when they coincide, the recording pen 14 is made to operate to conduct recording on the recording paper 15.