SU546818A1 - Ultrasonic device for automatic measurement of flow rate - Google Patents

Description

one

This invention relates to technical acoustics and can be used to control the flow rate of liquids and gases.

Ultrasonic flow velocity meters are known, having two acoustic transducers placed in the measured flow, one of which is used to determine the ultrasound velocity along the flow and the other upstream, the difference of these velocities determines the flow velocity (1-5). However, these meters have not sufficiently high accuracy either due to the mutual influence of the acoustic parts of the channels along the flow and against it, or because of the errors introduced by the phase meter.

A single channel measuring device is known, which contains a measuring acoustic transducer with two sensors, two identical measurement channels, including a phase meter and a modulator, whose inputs are connected to the generator output, and the second input of the phase meter is connected to the sensor and the modulator output of another channel, a switch with two outputs , each of which is connected to the control inputs of a phase meter and a modulator of one channel, and a recording device (6).

However, this device has a lack of accuracy due to the nonlinearity of the amplitude and phase characteristics of phase meters,

as a result, a change in the sound CKopoctH in a liquid causes a drift of the starting point of the phase meter, which goes beyond the linear portion of its amplitude-phase characteristic.

To improve the accuracy of measuring the flow rate, the proposed device contains an integrator, the inputs of which are connected to the control inputs of phase meters, and the output - to the input of the generator frequency adjustment, two relays, whose inputs are connected to the outputs of phase meters, and the outputs - with two inputs of the switch, the third output of which connected to the control input of the registering device, the measuring input of which is connected to the output of the generator.

FIG. 1 is a block diagram of the described device; in fig. 2, 3 - amplitude-phase and amplitude-frequency characteristics of the phase meter.

The device contains an acoustic measuring transducer with two sensors 1, a generator 2, modulators 3, 4, phase meters 5, 6, a relay 7, 8, a switch 9, a recording device 10, an integrator 11.

Each of the two measuring channels consists of a modulator 3 (4), a phase meter 5 (6), and a relay 7 (8).

The output of the integrator 11 is connected to the frequency tuning input of the generator 2, the output of which is connected to the measuring input of the registering device 10 and to the inputs of the modulators 3, 4 and phase meters 5, 6. In each channel the output of the modulator 3 (4) is connected to the corresponding sensor measuring acoustic transducer 1 and with the second input of the phase meter 6 (5) of another channel.

The output of phase meter 5 (6) is connected to relay 7 (8).

The outputs of relay 7 and relay 8 are connected to a switch 9, the nerve output of which is connected to the control inputs of the modulator 3 and the phase meter 5 of one channel, and the second to the control inputs of the modulator 4 and the phase meter 6 of the other. The first and second outputs of the switch 9 are connected to two inputs of the integrator 11. The third output of the switch 9 is connected to the control input of the recording device 10.

The device works as follows. Suppose that in the initial state the measurement channel is connected to the flow. The output signal of a constant level from the switch 9 opens the modulator 3 and the phase meter 5. The same signal is fed to the first input of the integrator I, at the output of which a linearly decreasing voltage is formed, which, affecting the frequency tuning input of the generator 2, gradually decreases its frequency .

FIG. 3 curve 1 corresponds to the propagation of ultrasonic oscillations against the flow, and curve II - along the flow, I - the distance between the sensors.

When the frequency changes from f to / at the output of the phase meter 5, the voltage will take a zero value k times, where k is an integer (see Fig. 3, curve II).

Relay 7 generates short square voltage pulses corresponding to zero values of the output voltage of phase meter 5. These pulses go to switch 9, which opens registering device 10 to measure the frequency of generator 2 at the times corresponding to the first and k-ouy output pulses relay 7 (8). Moreover, the frequency / + of the generator 2, corresponding to the first pulse, increases the readings of the recording device, and decreases the fe-ohm. At the output of the recording prioor, the difference in frequencies f f k is fixed, which is proportional to the speed of ultrasound C from one sensor to another.

With Co 4-,

where Co is the ultrasound velocity in the medium,

V is the flow rate.

Under the action of the 7th pulse at the output of the relay 7, the switch 9 opens the modulator 4 and the phase meter 6, i.e., the upstream measuring channel is connected. At the same time, the output voltage from switch 9 is fed to another input of integrator 11. A linearly increasing voltage is generated at its output, which gradually increases the frequency of generator 2. At the output of relay 8, pulses occur, corresponding to zero values of the output signal of phase meter 6. Recording device 10 measures the frequency of the / and / - generator

2. The readings of the registering device 10 at the moment of action of the 1st impulse increase, and under the action of k-from - decrease. At the same time, at the output of the registering device 10, the difference in the ultrasonic velocities along the flow and against the flow, i.e., the measured velocity V, is recorded.

The switch 9 after the impact of the pulse from the relay 8 switches on the measurement channel along the flow, i.e., opens the modulator 3 and the phase meter 5. The device returns to the initial state and the measurement cycle repeats again.

The presence of an integrator 11, generating a linearly varying voltage, according to which the frequency of the generator 2 varies within certain limits, two relays 7, 8, producing square pulses at zero voltage at the output of phase meters 5, 6, makes it possible to use a phase meter as zero phase difference indicator.

This eliminates the influence of the nonlinearity of the amplitude-phase characteristics of the phase meter, which improves the accuracy of measuring the flow velocity. Fixing k null points at the output of phase meters allows k measurement error to be reduced by a factor of k.

The width of the amplitude and phase characteristics of the phase meter does not constitute an upper range of measured flow velocities in the proposed device, which makes it possible to increase it in comparison with the known devices.

Claims (1)

Invention Formula An ultrasonic device for automatically measuring the flow rate, comprising a measuring acoustic transducer with two sensors, two identical measuring channels, including a phase meter and a modulator, the inputs of which are connected to the generator output, and the second phase meter input connected to the sensor and the modulator output of the other channel two outputs, each of which is connected to the control inputs of a phase meter and a modulator of one channel, and a recording device, characterized in that, in order to increase the accuracy of measurement At a flow rate, the device is equipped with an integrator, the inputs of which are connected to the control inputs of phase meters, and the output to the frequency tuning input of the generator, two relays whose inputs are connected to the outputs of phase meters, and the outputs to two inputs of the switch, the third output of which is connected to the input of the recording device, the measuring input of which is connected to the output of the generator.