GB1290978A - - Google Patents

Abstract

1290978 Ultrasonic thickness measuring AUTOMATION INDUSTRIES Inc 2 Sept 1970 42038/70 Heading H4D A transmitter causes a first transducer to emit ultrasonic energy and a receiver responds to echoes from the first and a second transducer and passes them through a common channel to a measuring means which produces two signals representing the time delay between the transmission pulse and the receipt of energy by said first and second transducers respectively. Pulse generator 44 produces a synchronizing ("sync.") pulse which sets bi-stable 48 and A-D converter 50 to zero and sets bi-stable 40 to close the upper input of gate 38 and the upper output of gate 54. After a delay of 10 ms. converter 50 passes this pulse to main sync. generator 34 which produces two spaced pulses. The first of these pulses changes the state of bi-stable 40 thereby reversing the states of gates 38, 54. Pulser 32 also produces a transmit pulse for transducer 24 which pulse also passes through gate 38 to the receiver where it eventually sets bi-stable 48. Since transducer 26 is isolated by the gate 38, the echo from the top surface of specimen 12 is passed through gate 38 to reset bi-stable 48. The bi-stable output is connected to a ramp generator which thus produces an output whose peak amplitude represents the echo flight time. This is detected by peak detector 56, selected by bi-stable 40 and passed to one input of differential amplifier 58. The second pulse from generator 34 is similarly treated but due to the switching of bi-stable 40, the echo comes from the bottom surface of specimen 12 via transducer 26. Peak detector 60 applies the peak amplitude to the second input of differential amplifier 58 which thus produces an output representing the specimen thickness. Converter 50 produces a pulse whose width is proportional to the amplifier 58 output amplitude and this pulse operates clock 62. The number of output pulses therefrom is counted by counter 64 which is calibrated directly. The pulses are also displayed on a C.R.T. The transducers are mounted in a unit 20 of soundabsorbing material and are displaced from the specimen surface thereby. They are also arranged such that their directional patterns overlap at the specimen bottom surface.