SU964542A1 - Flow rate meter - Google Patents

Description

(54) FLOW SPEED METER

The device relates to ultrasonic technology and can be used, in particular, to monitor and measure the flow rate of flowing media, as well as the speed of movement of bodies in these media.

A single-channel flow rate meter is known, based on a phase method, containing a series-connected generator, radios and receiving electroacoustic transducers, a phase meter, the second input of which is connected to the generator output via a phase shifter. The principle of operation of this meter is based on measuring the phase difference of the emitted oscillations and oscillations transmitted at an angle other than 90 to the vector of the flow velocity of the flowing medium (the known distance from the electroacoustic emitting converter to the receiving one) ij.

The disadvantage of this device is the large measurement error. This is due to the fact that the detected difference in the phases of the signals depends not only on the velocity of the flow, but also on the temperature and concentration variations of the slope. ultrasound.

The closest in technical essence to the invention is a device containing two electro-acoustic channels, each of which consists of radiating and receiving. electroacoustic transducers, generator, phase shifter and phase meter 2}.

Phase variations of the signals on the receiving transducers, caused by the flow velocity, are obtained close in magnitude and OPPOSITE in sign. At the same time, phase changes due to temperature

15 or concentration changes in the speed of ultrasound in the environment, are equal in sign and close in magnitude. In this regard, in the device, an increase in the dependence

20 phase difference signals (and hence the voltage at the output of the phase meter) at the receiving transducers on the magnitude of the flow velocity and the weakening of the dependence on temperature

25 and concentration changes in the speed of ultrasound. However, the effect of temperature and concentration changes in the speed of ultrasound in a known device cannot be greatly weakened.

30 due to the limited possibilities of equalizing the average values of the wave lengths of the rays in the channels by mechanically changing the position of the electroacoustic transducer

It is known that it is difficult to ensure the accuracy of mechanical movements, especially at frequencies of ultrasonic oscillations greater than 1 mG. As a result of the large errors of the mechanical installation, an uncompensated mean difference in the paths of the rays in the channels appears, because of which the output voltage is strongly dependent on temperature and concentration. changes in the speed of ultrasound, which limits the accuracy of the device, especially when it is used in environments with a large range of changes in the speed of ultrasound.

The aim of the invention is to improve the measurement accuracy and simplify the setup process of the device.

The goal is achieved by the second generator, the first and second mixers, the first and second low-pass filters, the second generator is connected to the second radiating electroacoustic converter, the inputs of the first mixer are connected to the generator outputs, and its output through the first low-pass filter and phase shifter. connected to one of the inputs of the phase meter, the inputs of the second mixer are connected to the receiving electroacoustic transducers, and its output through the second low-pass filter chen to the second input of the phase meter.

The drawing shows a block diagram of the device.

The device contains two generators 1 and 2, connected to two electro-acoustic channels, consisting of radiating 3 and 4 and receiving 5 and b electro-acoustic transducers kashdai, series-connected first mixer 7 and low-pass filter 8 and second mixer 9 and low-pass filter 10. Inputs of the first mixer 7 is connected to the radiating 3 and 4, and the inputs of the second mixer 9 - to the receiving 5 and b electroacoustic transducers. The outputs of the low-pass filters 8 and 10 directly and through the phase shifter 11 are connected to the inputs of the phase meter 12. The output of the phase meter 12 is the output of the device.

The device works as follows.

High frequency oscillations i and A sinu; generators 1 and 2 are supplied to radiating electroacoustic transducers 3 and 4 and to the inputs of the first mixer 7. Excited by radiating transducers 3 and 4. ultrasonic waves pass through the medium under study and fall on receiving electroacoustic transducers 5 and b, which convert them into electrical oscillations

-) +

Vo

Vie va

Jfcaj-e,

(1 +

receiving and receiving electroacoustic transducers in the singing and in the second channels;

.Vp is the average velocity of ultrasound propagation in the medium;

/ - composing ultrasound velocity, due to Lenna temperature

and concentration changes in the medium; V is the flow rate of the medium;

(is the angle between the flow velocity vector and the ultrasonic beams in the channels; A, AJ are the oscillation amplitudes.

From receiving electroacoustic transducers, the signals go to the second mixer 9. The product of multiplying the signals in mixer 9 is oscillations with a frequency and phase equal to the difference in frequency and phase of the input oscillations, as well as oscillations with a frequency and phase equal to the sum of the frequencies and phases of the input oscillation. However, only the oscillations of the difference frequency and phase pass through the second low-pass filter 10 to the input of the phase meter 12.

0, ni -a.a.) t, Vk

)(one

Vo

The second input of the phase meter 12, having passed the first low-pass filter, 8 and the phase shifter 11 (used for the initial setting of the phase meter zero), receives the oscillations of the difference frequency and phase from the output of the first mixer 7,

and 0,5A..A, sinr (ie -) t. V

At the output of the phase meter, a voltage occurs that is proportional to the phase difference of the signals at its inputs.

Vcosoi

(+ U / 2 L) +

(Lg lz

V, -vr

component of this is a direct signal)

V with Sg

- (ЧЦ

+ u.4) v

2t2Vcosoiu LVp

directly proportional to flow velocity, second

It turns out to be equal to the ratio of the relative error of the alignment of the distance between the radiating and receiving electroacoustic transducers in channels E1-L and the relative errors of 2A- and / -; frequency setting.

The device allows significantly

10 to improve the accuracy of flow rate measurement.

Claims.

15

0 o

The effect of changes in the ultrasound velocity on the measurement results can be made arbitrarily small, and, consequently, an increased measurement accuracy is ensured.

For proof, we find the magnitude of the gain in measurement accuracy.

The relative error cG measurements of the flow rate using a known device is equal to

UH

(f- & L Vc L 2Vcos 6

The relative error of the measurements with the help of the offer is equal to

, TO UK ° W Vcosci

The magnitude of the gain in precision measurements, defined as

uL

SG i:

AT

-77-

2 o

A flow rate meter containing two electroacoustic channels, each of which consists of radiating and receiving electroacoustic transducers, a generator, the output of which is connected to one of the radiating electroacoustic transducers, a phase shifter and a phase meter that differs

By the fact that, in order to improve the measurement accuracy and simplify the tuning process, a second generator, first and second mixers, and first and second low-pass filters were introduced, the second generator connected to the second radiating electrically acoustic converter, the inputs of the first mixer were connected to the outputs of the generators and his exit

through the first low-frequency filter and the phase shifter is connected to one of the inputs of the phase meter, the inputs of the second mixer are connected to the receiving electroacoustic transducers, and its output through the second low-pass filter is connected to the second input of the phase meter.

45 Sources of information

take into account when examining

N.I. Ultrasonic Energy, 1968,

USSR certificate

01 R 5 / 00,1955 (about

Claims (1)

Claim. A flow velocity meter containing two electro-acoustic channels, each of which consists of a radiating and receiving electro-acoustic transducers, a generator, an output. which is connected to one of the emitting electro-acoustic transducers, ¹ phase shifter and phase meter, characterized in that, in order to improve the measurement accuracy and simplify the tuning process, a second generator, first and second mixers and first and second low-pass filters are introduced into it, the second generator connected to the second emitting electro-acoustic transducer, the inputs of the first mixer are connected to the outputs of the generators, and its output through the first low-pass filter and phase shifter is connected to one of phasemeter moves, inputs are connected to the second .smesitelya receiver electroacoustic transducers, as its output through the second low-pass filter connected to the second input fazomet pa.