SU503130A1 - Ultrasonic flow meter - Google Patents

Description

one

The invention relates to ultrasonic measurement methods and can be used to determine the flow rate of a liquid or gas and its flow.

Ultrasonic flow meters are known, based on the effect of ultrasonic waves displacing a liquid or gas flow and containing high-frequency oscillators, coupled with radiating vibrators that excite downstream and downstream oscillations, receiving vibrators, electric oscillation mixers and a measuring unit.

The disadvantages of the known devices are the dependence of the measurement results on the change in the velocity of propagation of ultrasonic vibrations in a moving medium, as well as the low accuracy of measurement of the current flow rate. To obtain high accuracy with a large measurement base, the measurement time should be significantly increased, which eliminates the control of the current flow.

To improve the measurement accuracy, the proposed flow meter additionally contains a sawtooth generator, the high frequency oscillator being connected to the radiating vibrators, the emitters of one channel and the receiving vibrator of the other are connected to the inputs of each mixer, and

The mixers are connected to the inputs of the measuring unit, one output of the sawtooth generator is connected to the frequency control input of the high frequency oscillator, and the other to the enabling input of the measuring unit.

In addition, the measuring unit can be made in the form of a reversible counter, two outputs of which are connected via keys to

a pulse generator and electric oscillation mixers, and the third input of which is connected to the third inputs of the keys and to the sawtooth generator.

FIG. 1 shows a block diagram of an on-write device; in fig. 2 - timing charts of signals at various points in the block diagram.

The flow meter contains a two-channel acoustic transducer with radiating G, 2

and receiving 3, 4 vibrators, which are fixed on the pipeline 5, the generator 6 high-frequency oscillations connected to the radiating vibrators 1, 2, mixers 7 and 8 electrical oscillations, to the inputs of each

Claims (2)

of which, respectively, the radiating vibrator 1 (2) of one channel and the receiving vibrator 3 (4) of the other, are connected, the measuring unit 9, the inputs of which are connected to the outputs of mixers 7 and 8, and a sawtooth voltage generator 10, one output of which is connected to the input of frequency control generator 6 high-frequency oscillations, and the other - with the enable input of the measuring unit 9. The measuring unit 9 contains keys 11 and 12, a pulse generator 13 and a reversible counter 14. Two inputs of the reversing counter 14 are connected to a pulse generator 13 and a mixture ate E 7 and 8, and the third input - to a third input keys 11 and 12 and the generator 10. The apparatus works as follows. The sawtooth voltage of the oscillator 1C changes the frequency of the ultrasonic oscillator 6 according to the sawtooth law (Fig. 2a). From generator 6 are high frequency. voltage oscillations with varying frequency are supplied to radiating vibrators I and 2, exciting ultrasonic oscillations along and against the voltage of the flow medium 15 e of the pipeline 5. On receiving vibrators 3 4 ultrasonic oscillations arrive with a shift by time n and T2, respectively, , -. T2 (1) С + Vс-V The variation of the oscillation frequency with time at the receiving vibrators 3 and 4 (at the points of the scheme of Fig. 1) is shown in FIG. 2d and 2d respectively. The input of mixers 7 and 8 is supplied with the voltage of a varying frequency from the high-frequency oscillator 6 (Fig. 2a), and the voltage of the varying frequency from the receiving vibrators 3 and 4 (Fig. 2d and 2e), respectively. Since the voltage of the varying frequency in the receiving vibrators 7 and 8 is shifted by the time n and T2 relative to the emitted oscillations (Fig. 2a), the difference frequency at the output of the mixer 7 will be equal to b /. T a and the difference frequency at the output of the mixer is where / is the maximum deviation of the frequency of the generator 6 ultrasonic oscillations over a period of time T. The voltage difference of the difference frequency at the output of the s-meter (point g of the circuit of fig. 1) is shown in fig. 2, at the output of the mixer 8 (point e of the circuit of FIG. 1) -at FIG. 2nd. We denote the period of the difference frequency at the output of the mixer 7 by TI, and at the output of the mixer 8 by Gd. At the same time, from expressions (1), (3) we find that the difference between the periods of difference frequencies is 1 t / I 1 11 JII -7; (- - 2 - L t, e. With the linear modulation law R. two difference frequencies directly 45 50 55 60 65 are pertinent to the flow rate V and do not depend on the speed of ultrasound in the medium under study 15. Measuring unit 9 is used to measure the period difference by expression (4). Permitting input (point b in Fig. 1) measuring unit 9, a signal is supplied from the second output of the generator 10 to set the measurement time (time diagram of the signal shown in Fig. 26). The measuring unit 9 uses a reversible counter 14, a pulse generator 13 and two keys No 12. A pulse generator 13 supplies the key AND the pulses of a stabilized frequency (Fig. 2n), and the key 12 - the pulses of the same frequencies but shifted by a part of the period so that the pulses at the output of the key 11 do not coincide in time with the pulses at the output of the key 12. The generator 10 resets the reversible counter 14 to the zero state and produces the enable pulses at the inputs of the keys 11 and 12 (at the points b) shown in FIG. 26. Under the action of the signal of mixers 7 and 8 (fng. 2 g and 2 e), the second inputs of keys II and 12 form a resolution impulse for the time period G and TZ, respectively (Fig. 2k and 2i). Therefore, to each input of the reversible pulse counter 14, a burst of pulses from a pulse generator 13 is supplied, the number of pulses in the first burst (FIG. 2H) is proportional to the period TI, and the pulse count in the second burst (Fig. 2m) is Tj. Consequently, the readout of the reversible counter will correspond to the difference between the periods of the two difference frequencies and will be proportional to the flow velocity by expression (4). In measuring unit 9, it is possible to measure not only one period, but also a half-period or several periods or half-transitions of difference frequencies 6/1 and 6/2. 1. Ultrasonic flowmeter comprising a two-channel acoustic transducer with radiating and receiving vibrators in each channel, a high-frequency oscillator, two electric oscillation mixers, and a measuring unit, characterized in that, in order to improve the measurement accuracy, the device additionally contains a generator a sawtooth voltage, with the high-frequency oscillator connected to the radiating vibrators, respectively, each radiator is connected to each mixer ibratrr one another and the receiving vibrator, vyhedi CITEL's house are connected to inputs izmeritelnogd block odrn pilorbraznogd generator output voltage is connected to the input of the frequency adjustment gen§ratore vysekochastotndh ranging nry and the other - with the enabling input tonnage NC unit. 2. The device according to claim 1, characterized in that the measuring unit is in the form of a re A counter, whose two inputs are connected via keys to a pulse generator and electric oscillation mixers, and the third input of which is connected to the third inputs of the keys and to the sawtooth generator. , f