JPS6235062B

PURPOSE:To measure the hardening characteristic of a hardened material continuously with a high precision on the basis of change of the sound velocity by a constitution where a sample vessel, acoustic wave transmission part and receiving part, an acoustic wave propagation time measuring circuit, a mechanism which corrects automatically the distance between the receiving part and the transmission part, and a display equipment are connected. CONSTITUTION:An acoustic wave transmission part is constituted by pulse transmitter 1 and oscillator 2 which puts pulses of transmitter 1 into sample 10 as sound, and the acoustic wave propagated through sample 10 is received by receiver 3, and the time difference between the signal from transmitter 1 and the signal from the receiving part is corrected by time difference correcting circuit 6. Expansion and contraction detector 7 which detects electrically change of the length between transmitter 2 and receiver 3 and distance correcting circuit 8 which corrects the signal from time difference correcting circuit 6 into a detection value corresponding to a prescribed length before expansion and contraction are provided as measurement distance correcting mechanisms, and thus, measurement in all processes of hardening can be performed with a high precision and be displayed finally as a signal on display equipment 9.