SU792077A1 - Medium velocity ultrasonic meter - Google Patents

Description

one

The invention relates to a measurement technique and can be used to simultaneously measure the speed of movement of the medium and the speed of ultrasound in it or a parameter depending on 5 of the speed of ultrasound: temperature, pressure.

A pulsed ultrasonic thermo-anemometer is known in which the measurement of the flow velocity is made by measuring the frequency difference between the pulse-modulated ultrasonic oscillations propagating in two opposite directions in the closed dynamic system of the device l. 15

It allows you to measure the speed of ultrasound in the medium and the speed of the medium, however, the accuracy of the measurement is influenced by both the non-identity and instability of both electrical channels, and the instability of the front and rear edges of pulses, as well as fluctuations, as the medium is probed by both directions at different points and optionally one at a time. 25

A known cylinder ultrasonic velocity measuring device containing transceiver elements placed on opposite walls of the channel at an angle to the direction U

flow, an amplifier, a mixer, a low-pass filter, a driver, a controlled electronic pulse counter, and a oscillating frequency generator modulated according to a sawtooth law, connected to the high-frequency output with an input to the directional muffler, the outputs of which are connected to the transmitter and receiver. elements and inputs of the mixer, while the output of the directional switch is connected through an amplifier to another input of the mixer connected to the input through a low-pass filter to the input of the measuring circuit Iodine, the low-frequency output of the kachayugtsay frequency generator is connected via a driver to the inputs of a direction switch, the input of a measurement period selection circuit and the input of a pulse counter control circuit whose outputs are Count, Start and Stop connected to the corresponding inputs of a controlled counter, and the output of a sweeping frequency generator is connected to one from the inputs of the measurement period allocation circuit 2.

With this meter, only one parameter is measured: speed i

environment. In addition, the medium is in each direction at different times, and the magnitude of the fast fluctuations of the velocity of the medium or the velocity of ultrasound in the medium is not compensated, which introduces a measurement error. . The purpose of the invention is the simultaneous measurement of the speed of ultrasound in the medium and an increase in accuracy.

This goal is achieved by the fact that an ultrasonic measuring device for the velocity of a medium is equipped with a series circuit of a high-frequency filter and a period-voltage converter connected between the output of the mixer and an ultrasound velocity indicator in the medium and a calculator in the form of serially connected waiting generator of stable duration and amplitude, selector and accumulator, with. Thereby, the high and low frequency filter outputs are respectively connected to the start input of the waiting generator and the selector input, the control unit for communication with the selector and the accumulator, and the indicator of the velocity of the medium, made in the form of a DC ratio meter, is connected between the output of the calculator and the indicator ultrasound velocity in the medium.

The drawing shows a structural diagram of the meter.

A high-frequency voltage generator 1 with linear frequency modulation with control unit 2 is connected to one of the inputs of switch 3, to the middle contact of which electroacoustic transducers 4 and 5 are located, located at a distance of b. The other input of the switch 3 is connected via amplifier b to the input of the mixer 7, and the other input of the mixer 7 is connected to the generator 1. To the output of the mixer: a series circuit from the high-pass filter 8 and a converter period-voltage 9 are connected, to the output of which indicator 10 is connected ultrasound velocity in the medium.

The output of the mixer through the low-frequency filter 11 is connected to the selector 12 of the transmitter, made as a series-connected standby generator 13 of stable duration and amplitude pulses, the selector 12 and the accumulator 14. The output of the filter 8 is also connected to the trigger input of the generator 13, and the output of the calculator through the indicator 15 speeds of movement of the medium - with ultrasound speed indicator 10. Control unit 2 is connected with generator 1, switch 3 and blocks 12 and 14 of the calculator. .

The meter works as follows.

The voltage of the generator 1, whose frequency under the influence of the control unit 2 varies according to a straight-line law, is sent to one of the inputs of the switch 3. The switch 3 periodically connects the electro-acoustic converters 4 and 5 to the output of the generator 1 (on a time less than the running time of the ultrasound of L) or j to the output of the amplifier 6. The ultrasonic waves are emitted from the transducers towards each other and reach them with T and Tg backlashes equal to; T - - t - b

H c + vi

(1) where. C is the speed of ultrasound in a stationary medium; V is the projections of the velocity of the medium on the direction of propagation of ultrasound.

The frequencies f and the signals received and converted by converters into electric voltage are respectively:

U)

 . . -.

where f V, the frequency of the ultrasound transmitted at a given time,

K - coefficient of proportionality, equal to the rate of change of the frequency of the generator 1.

Both oscillations are summed at the input of amplifier 6. Because of the beating between the combinations, the signal at the output of amplifier b is a sinusoidal electric frequency oscillation, h, whose amplitude varies from a minimum (equal to zero if both signals are of the same amplitude) to a maximum of frequency fi p -This signal is fed to one input of the mixer 7, to the other input of which the signal of the generator 1 is supplied with the frequency If, Due to the beats between the signals of the frequencies fy, and the modulus of the total signal undergoes double changes from minimum to maximum:

low frequency with frequency:

. high frequency;

. but

not continuous oscillations emitted by a burst of pulses emitted from it are actually emitted. However, this circumstance has no effect if the switching frequency of the switch is much higher than Fg. : Formulas Ij and 2 imply the following dependencies (with an error of the order of):

.TB;

Fb

(four)

 2К.Ь

Claims (2)

where Tg, TH are the periods of high-frequency and low-frequency beats, respectively. The pa outputs of Mixer 7, which in the simplest case consists of a sum, a phase and an amplitude detector, selects a signal containing the frequencies fc and. The signal with frequency F is emitted by high-pass filter 8 and; through the transducer period-voltage} :: en 9 enters the indicator 10 of the ultrasound velocity in the medium. A signal with a frequency f is extracted by a low-frequency filter 11 and fed to a selector 12. With each period of high-frequency beats, an oscillator 13 is triggered, producing pulses of stable duration and amplitude. Under the influence of signals from the outputs of the low-frequency filter 11 and the control unit 2, the selector 12 transmits to the input of the accumulator 14 the pulses of the generator 13 for a time proportional to a given number of periods n of frequency beats of TC. The output voltage of the accumulator 14, built, for example, on the basis of an integrator, is propagated to the product Ti FB. Indicator 15 is the velocity of the medium movement, made in the form of a DC ratio meter, for example, a log-metric measuring instrument, proportional to the voltage proportional to, to a voltage proportional to Tj, Fa, t, c. can be calibrated in units of velocity. In the case of a measurement in a low-temperature environment, the ultrasonic oscillations in the distance I are slightly weakened and constitute a noticeable part of the emitted oscillations. The necessity of amplifying the received oscillations disappears and the switch 3 constantly connects the output of the generator 1 to the converters 4 and 5. The rest of the meter operation is similar to that described above. The meter is prepared for the next measurement cycle by resetting the selector 12 and the accumulator 14 to the initial state with the corresponding signals of the control unit 2. Claims of the Invention An ultrasonic measuring device for the velocity of a medium, comprising a generator with a linear frequency modulation, connected via a switch with electroacoustic transducers, connected to a switch, a series of amplifiers, a mixer, a coupled input with a generator, and a low frequency filter, as well. a control unit connected to a generator and a cocator, and indicators of the speed of the device and the speed of the medium, characterized in that, in order to simultaneously measure the speed of ultrasound in the medium and improve accuracy, it is equipped with a series circuit of a high-frequency filter and a period converter between the mixer output and the ultrasound speed indicator and the transmitter in the form of series-connected waiting pulse generator of stable duration and amplitude, selector and drive , While the outputs of high and low frequency filters. respectively connected with. the start input of the waiting generator and the selector input, the IV control unit is connected to the selector and accumulator, and the movement speed indicator, made in the form of a constant-voltage ratio meter, is connected between the output of the calculator and the ultrasound speed indicator in the medium. Sources of information taken into account in the examination 1. The author's certificate of the USSR 134920, cl. G01 P 5/00, 1959. 2. Authors certificate of the USSR 494693, cl. G01 P 5/00, 1973 (prototype.