GB1260388A - Measuring device - Google Patents

Abstract

1,260,388. Ultrasonic inspection devices. NEDERLANDS APPLIED SCIENTIFIC RESEARCH FOR INDUSTRY, TRADE & COMMERCE. 31 Jan., 1969 [2 Feb., 1968], No. 5402/69. Heading H4D. In a system for measuring a time interval a mechanical impulse is applied to a test body and a reply signal is received from the body, electrical pulses respectively phase-related to the generation of the mechanical impulse and reception of the reply pulse are generated and applied respectively to set and reset a bi-stable circuit, the bistable output controls the supply of clock pulses to a counter for measuring the time interval, and a delay unit is arranged to delay the start of the counter, in relation to generation of the mechanical impulse, by an adjustable correction time. In the Fig. 1 embodiment, for measuring ultrasonic propagation time (hence wave velocity, which is a measure of the elasticity modulus and material strength) through a concrete specimen, magnetostrictive transmitter transducer A is pulsed by firing thyristor 23 and at the same time generates an electrical pulse (in winding 3) for triggering monostable circuit B and bi-stable circuit C. Piezoelectric receiver transducer D output is applied via amplifier 5, threshold amplifier 6 and gate F to reset the bistable C. Monostable B output blocks gate F while the ultrasonic pulse is being generated, to prevent electrical disturbances from resetting bi-stable C. While bi-stable C is in its triggered state, clock pulses from generator G are fed via gate H to decade counter-tube readout device K. To compensate for the ultrasonic propagation time in members which couple the specimen to transducers A and D, device K is prevented from starting to count until a preset period determined by a further monostable circuit L has elapsed. Circuit details of the apparatus are given.