SU777438A1 - Automatic ultrasonic flowmeter - Google Patents

Description

move to the reference inputs of the phase meter and temporary discriminator, the signal input of the phase meter is connected to the switch output, the control input of the temporary discriminator is connected to the fifth output of the control unit, and the outputs of the time discriminator are connected to the single input of one trigger and through an inverter to the zero input of another trigger , the second inputs of two triggers are connected to the sixth output of the control unit, and the outputs of two triggers and a phase meter are connected to the inputs of an adder, the output of which is connected to the inputs of two keys.

FIG. 1 shows a structural diagram of an automatic ultrasonic flow meter; in fig. 2 - time diagrams of voltages at individual nodes of the circuit; in fig. 3 shows time diagrams of voltages on piezoelements and static characteristics of a phase meter, time discriminator, and summator.

Automatic ultrasonic flow meter contains two installed on the pipeline / piezoelectric element 2 and 3 connected to the switch 4, including, for example, two pairs of serially connected keys 5, 6 and 7, 8 with connecting the output of the key 5 to the piezoelectric element 2, and the output of the key 7 to the piezoelectric element 3, the shock excitation generator 9, the output of which is connected to the inputs of the keys 5 and 7, the control unit 10, consisting, for example, of two keys // and / 2 and serially connected pulse distributor 13, whose input is connected to the output 1m of the keys // and 12, and tr the gage 14, the additional switch 15 turned on at the output of the shock excitation generator 9, the phase meter 16 and the time discriminator / 7, the signal inputs of which are connected to the outputs of the keys 6 and 8, and the reference inputs to the output of the additional switch 15, are connected to the output of the phase meter the inputs of the adder 18, and the outputs of the time discriminator 17 are connected to the input of the inverter 19 and the single input of the trigger 20, the output of the inverter 19 is connected to the zero input of the trigger 2-1, the output of which, like the output of the trigger 20, is connected to the input of the adder 18, two chain consisting u E from the series-connected key 22 and the controlled generator 23, as well as the key 24 and the controlled generator 25, which are connected at the output of the adder 18, the outputs of the controlled generator 23 and 25 are connected to the inputs of the frequency meter 25 and the keys // and 12 of the control unit 10 The output "a of the control unit 10 is connected to the control inputs of the keys 5, 8, 12 and 22, the output" b - control inputs of the keys 6,7, 11 and 24, NX10D "-C - to the input of the generator of shock excitation 9, output" d - to the control input of the key 15, outputs: one "e - to the control input of the temporary discriminator 17 and the output" f - to zero vomu Valid Trigger 20 and trigger unit 21 entry.

Automatic ultrasonic flow meter works as follows.

When the flow rate V changes (see Fig. 2), for example, an increase in the ultrasound velocity along the C + Vcosa stream and a decrease against the flow occurs.

C-Vcosa, where C is the speed of ultrasound in a stationary medium, and is the angle between vectors C and V. The proposed device is used to measure the flow rate (velocity V) in two cycles. In one cycle, the ultrasonic velocity along the flow is measured and converted, and in the other cycle the ultrasonic velocity is measured and converted into the frequency, the difference between the indicated frequencies is proportional to the measured value of the velocity of flow V.

Let the trigger il4 of the control unit 10 is in such a state that the voltage Ui (a) (see Fig. 2) from the output opens keys 5 and 5 of the switch 4 and the keys 22 12 at the input and output of the controlled generator 23 The output signal "b trigger 14 keys 6, 7, 24 and: 11 are locked. Thus, the following automatic

The system is connected to measure the speed of ultrasound downstream. The pulses / 2h of the controlled generator 23, which carry out the switching of the outputs of the control unit W through the switch 12, are fed to the input

pulse distributor 13. Suppose that the maximum number of pulses in this cycle is seven. The specified number of pulses is selected based on the design of the acoustic part of the flow meter

and acoustic properties of the medium (the smaller the attenuation of ultrasound in the medium, the greater the number of pulses).

When a second pulse arrives at the input of the pulse distributor 13, a pulse arises at its output, c, the excitation generator of shock excitation 9, a voltage pulse f / g is formed, filled with high-frequency voltage

the phase of which is rigidly connected with the leading edge of the pulse. At the same time, a pulse (e) comes from the output of the pulse distributor 13, which prepares the time discriminator 17. The high-frequency pulse of the shock excitation generator 9 through the switch 5 of the switch 4 enters the piezoelectric element 2 in the form of a voltage U, which emits an ultrasonic medium impulse passing

through the flow of the medium at an angle a. The pulse is received by the piezoelectric element 3 through pro /

- where / is the time lag

C + Fcos and the standing between piezoelectric elements 2 and 5. Pulse voltage f / 3 from piezoelectric element 3

five

through the key 8 is applied to the signal inputs of the phase meter 16 and the time discriminator / 7. The third impulse of the controlled generator 23 is formed from the output "d will distribute (with the pulses of 13 the voltage pulse Uiz (d), which opens the key 15. At the same time, the signal c

the output from the pulse distributor 13, the shock excitation generator 9 generates a second high-frequency pulse f / g, coming through the open key 15 on, the reference inputs of the phase meter / 5, and the time discriminator 17. On the phase meter 16, the time shift is transformed Dt (om. Fig. 3 , a) between high-frequency oscillations, which fill the signal and reference pulses, at a voltage / le in accordance with the static characteristic of the phase meter 16 (Air) shown in FIG. 3, b. The static characteristic of the phase meter 16 has ambiguity, which is corrected by the time discriminator 17, inverter 1, and flip-flops 20 and 21. The temporal discriminator ./7 converts the time shift, -dt to pulse voltage f / iy, the amplitude of which in accordance with its static characteristic (see Fig. 3, b) is proportional to Dt, appearing on the first

or the second output of the temporary discriminator 17, depending on the polarity. The positive pulse Un from the first output of the temporary discriminator P17 enters the single input of the trigger 20, which translates it into another steady state, and as a result the leading edge of the pulse f / 2o is formed. If the pulse is Un of negative polarity, then from the second output of the temporary discriminator 17, the pulse f / 17 is sent to the zero input of the trigger 21 via the inverter 19. Together. The puppy relay characteristic of the trigger 20 and the trigger 21 with an inverter 19 is illustrated in FIG. 3, c. To dock the characteristics of the phase meter 16 (see Fig. 3, b) and the relay

- it is necessary that the trigger threshold of 20 or 21 is smaller than the maximum output signal f / ie of the phase meter 16. Signals from the phase meter 16 and the trigger .20 (or 2.1) are fed to the adder 18. The dependence of the output signal of the adder

- from the input value Dt (see Fig. 3, d) do not have ambiguity. The output signal of the adder 18 through the switch 22 performs first a coarse adjustment of the pulse-following period of the controlled generator 23 in the direction of reducing the output signal of the time discriminator 17 to the trigger threshold 20 (or 21), and then fine tuning of the controlled generator is performed in this way to reduce the output signal of the phase meter. down to zero. As a result, in the first step of measurement, the difference of the following imnv .TlbfTiR lHpp tchlarmpg uahrp tlp 9.9 T / h

becomes equal to the propagation time of the ultrasonic pulse downstream

., and the frequency of these IMC + V-cosa

pulses equal to

With + V-COSa.

F ,,

T ,,

When the pulse distributor 13 arrives at the input of the seventh pulse of the controlled generator 25, the trigger 20 is reset with the output pulse and the trailing edge of the pulse Uzo is formed, and the trigger 14 returns to another steady state. In this case, the elements of the flow meter are switched to the mode of conversion speed

ultrasound versus C – V flow - cqsa per pulse frequency of controlled oscillator 25.

The operation of the device in the second measurement cycle is similar to the first.

As a result, in the second measurement cycle, there is an accurate adjustment of the pulse follow-up period of the controlled generator 25 T25, which determines the correct propagation time of the ultrasonic pulses against the flow, -, -, ---, and often - V COS L

the following pulse is

C - Y-cos

one

, /

G ,.

Frequency meter 26 measures the difference between the frequency of the pulses at the outputs of controlled oscillators 23 and 25, the value of which is proportional to the velocity of the medium.

Claims (2)

1.Avtorsk) USSR certificate number 162335, cl. G 01 F 1/66, 1963. 2. US patent number 3720105, cl. 73-194A, 1973 (prototype). About 2, fi 5 to 7 Tiir ppppppppppppppp / t Uzs I I || 11 th y / fy / W: - /: , I I I ///// / U /// U // //////////////////// 7 7 / U Mr. Ih1in I iinrl 25 -t 2 3 ii 5 6 W V / 7 / Z W / p B I I I t iJ .-; -V UzfUy / 7