Abstract: A method of ultrasonic measurement of a rate of flow utilizes simultaneous passage of two auto-circulation pulse trains of opposite directions through a single acoustic channel and through the medium under control so that the instants at which the pulses of the trains are brought into coincidence are eliminated. The pulses of one pulse train are used to phase-synchronize a self-excited oscillator whose frequency is a whole number of times the repetition rate of such pulse train. The coincidence instants are eliminated by interrupting the same pulse train before a specific instant of coincidence and restoring it with the help of a pulse produced by the self-excited oscillator. The pulse is held out of coincidence with a pulse of the other pulse train. The rate of flow is the difference between the repetition rates of the pulses of the trains and is determined by comparing the repetition rate of the pulses of the other train with the frequency of the self-excited oscillator.

Abstract: In a method for discriminating the frequency difference of two pulse trains, the pulses of one train are separated into odd and even pulses, while in the second train every second pulse is separated. Then, every second pulse is checked for coincidence with even or odd pulses and, once such a coincidence occurs, the next check is for coincidence with, respectively, odd or even pulses, the frequency of such coincidences being representative of the frequency difference. In a device for discriminating the frequency difference of two pulse trains, a circuit for comparing one train with the other includes a separator of even and odd pulses, whose input serves as one of the inputs of the device.

Abstract: A method for triggering an ultrasonic flow meter comprising a synchronized ring circuit, consists of periodically turning the ring circuit on and off by trigger pulses whose repetition period is varied within the range of possible changes of the repetition period of autocirculation pulses of the synchronized ring circuit until an autocirculation pulse is matched with a trigger pulse. At such point, the application of trigger pulses to the synchronized ring circuit is discontinued by matching the frequency of the trigger pulses with that of the autocirculation pulses via continuous automatic phase control of the trigger pulse frequency. With no autocirculation pulses in the synchronized ring circuit, the application of trigger pulses is resumed.