GB1107015A - Ultrasonic pulse communication system - Google Patents

Abstract

1,107,015. Ultrasonic signalling systems. VACUUM REFLEX Ltd. 27 July, 1965 [1 Aug., 1964], No. 30413/64. Heading G4F. [Also in Divisions G1 and H4] The temperatures at three points under water are measured electrically in sequence and the corresponding values are transmitted through the water to a receiver and indicator on ship or shore by modulating the repetition frequency of short bursts of ultrasonic energy. Transmitter.-A ceramic ultrasonic transducer S1, Fig. 1, is energized by a resonant circuit T1 which is shock-excited by a silicon controlled rectifier SCR1, the repetition frequency of the output pulses being controlled by a relaxation oscillator comprising a unijunction transistor U1, capacitor C3 and resistor R2. In operation, the resistor shown as R2 consists of five resistors switched into circuit sequentially. The first is a fixed value resistor to provide a synchronizing signal which is of higher frequency than the measurement signals. The next three are the temperature sensitive resistors for measuring, and the last is a fixed value resistor to provide a calibrating signal equivalent to a temperature of 20‹ C. In a modification, Fig. 4 (not shown), an auxiliary circuit is provided to render the silicon controlled rectifier SCR1 non-conductive more rapidly after triggering so as to raise the frequency of operation. Receiver.-Ultrasonic pulses received at 1, Fig. 2, are converted to electrical signals, amplified, demodulated from the ultrasonic carrier and converted at 4 to square waves having a constant (10 millisecond) duration and a repetition frequency equal to that of the relaxation oscillator U1 &c. at the transmitter. The temperature measurement signals are passed by gate 14 to a counter 16 which counts the number of pulses occurring during a fixed measuring period which is determined by a bistable circuit 13, thus providing an output signal proportional to pulse frequency, i.e. proportional to the temperature sensed at R2. The counter 16 may be replaced by a ramp voltage generator operative for the period between two successive signal pulses. The three temperature measurements and the 20‹ C. fixed calibrating signal are displayed in turn., the particular channel in use being shown by lamps L1 to L4 controlled by a distributer 10 which is stepped progressively by short transmissions of synchronizing signal between each temperature transmissions. This synchronizing signal, which is of a higher repetition frequency than the measurement signals is detected at 5 and causes a shift pulse to be sent to the distributer 10 and also provides a signal to reset the counter 16 to zero before each measurement. At the commencement of each complete cycle of readings, the synchronizing signal is transmitted for twice the normal length of time, a condition detected by a delay network 7 and gate 8 so as to provide a reset signal for the distributer 10.