SU769337A1 - Ultrasonic frequency-time flowmeter - Google Patents

Description

The invention relates to the field of control and measurement technology, in particular, to the measurement of flow rate and the amount of liquid or gaseous media. Ultrasonic time-frequency flow meters, known for measuring the difference in the frequencies of two controlled oscillators, whose oscillation periods have been established (multiples the time of passage of ultrasonic pulses through the measured medium in the direction of flow and against it The closest in technical essence to the proposed is ultrasonic time-frequency spread one meter containing a measuring pipeline section with two transceiver converters, a switch, a discriminator, a shaper of probing signals, first and second next systems, first and second controlled generators, a differential signal extraction unit and an indicator, the switch connecting to the converters, the discriminator , by the output of the probing signal generator and the first inputs of the following systems, the second inputs — which are connected to the discriminator's output, the inputs of controlled generators are connected to the corresponding outputs of the following systems and with the outputs of the probing signal generator, and their outputs are the ic by the difference signal separation unit 2. The disadvantage of these flow meters is the large random component of the measurement error due to the passage of the 1 meter input of the differential frequency signal indicator caused by out-of-sync two generators, apr. and violation of the acoustic transparency of the controlled medium (gas bubbles in the controlled fluid, etc.), or not a controlled one of the following systems . The aim of the invention is to improve the accuracy of flow measurement. This goal is achieved due to the fact that the flow meter is equipped with the first and second triggers connected to the corresponding controlled generators and tracking systems, the first and second frequency discriminators and the three-input matching circuit, the inputs of which are connected respectively to the output of the differential signal extraction unit and through the corresponding frequency selectors are triggered, and the output is connected to the input of the indicator. The drawing shows a block diagram of an ultrasonic time-frequency flow meter.

The proposed flow meter contains a measuring section of pipeline 1 with integrated receiving and transmitting piezole transformers 2 and 3,; switch receiving and transmitting signals 4, time discriminator 5, shaper probing signals 6, tracking systems downstream 7 and upstream 8, first and the second controlled oscillators 9 and 10, the differential pulse frequency signal allocation unit 11, the first and second 5-triggers, 13 and 13, the first and second frequency discriminators 14 and 15, the three-input coincidence circuit 16 and the indicator 17.

The flow meter works as follows.

Depending on the clock cycle, the probe driver 6 receives alternately a sequence of pulses from controlled generators 9 and 10, one of which starts it.

During operation "downstream", one of the pulses of a sequence of controlled oscillator 9 and access to the input pho; distributor 6. Switch 4 directs a short probe pulse of the former 6 to the piezoelectric transducer 2, which operates as a radiator and converts the latter into an ultrasonic oscillation pulse distributed in the measured medium in the direction of flow.

Passing the measured Medium, the acoustic impulse arrives at the piezoelectric transducer 3, operating in this cycle as a reception of ultrasonic vibrations, which transduce the latter into an electrical signal sent by the switch 4 to the time discriminator S.

The time interval between the supply of a pulse to the driver 6 and the moments of registration of the receiving signal is compared by the tracking system 7 with the oscillation period of the controlled oscillator 9. The duration of this interval should. strictly comply with a certain number of half cycles of the frequency of the controlled oscillator 9.

This is achieved by working out a pulsed system with a impulsive system 7, which changes the frequency of the generator 9 towards usvedichen (genre L /) or decreasing (channel BI) until the moment of setting value when the impulse effects at the output of the following system alternate and arrive at separate inputs / 5-tr: itger 12, cause at its output pulse signals. The latter are transformed by the discriminator .14 into a resolving logical level of voltage supplied to one of the inputs of the three-input coincidence circuit 16.

When system 7 operates in transient conditions or when it is synchronized, its impulse effects follow only onHOMv from the channels and do not cause operation.

/ 5 flip-flops 12. In this case, the output of the frequency discriminator 14 leads to a prohibiting logic level of the voltage that enters the input of the circuit 16. To ensure stable operation, the time constant of the discriminator 14 is chosen to have a significantly longer flow time counter.

In the upstream cycle, the operation of the pacxho homer is similar to that described with the difference that the piezoelectric transducer 3 works as an emitter, and the piezoelectric transducer 2 - as a receiver. In this case, the input signal is formed.

L 6 is a pulse of the controlled generator 10, the frequency of the cat | 0 is controlled by the control of the following system 8, the alternation of pulses of which leads to the S-flip-flop 13, which causes the appearance of the permitting Lopian voltage level at the output of the frequency discriminator 15 arriving at the second input of the matching scheme, 16. The third input of the heme / 5 is the output of the block for the selection of a partial pulse-pulse spring and 11.

Thus, the differential pulse frequency signal carrying information about

flow rate or quantity of the measured medium, is fed to the input of the indicator device 17 only in the presence of permissive logical levels that arrive at the coincidence circuit 16 from frequency discriminators

14 and 15. This provides increased immunity of the device and increased: accuracy. measurements.

Claims (2)

1. Kremlevsky P. P. Flow meters and counters, M., “Mashinostroenie, 1975, p. 536. 2. Accepted for Germany application № 2517117, cl. G 01 F 1/66, 1975 (prototype).