SU347579A1 - Th flowmeter - Google Patents

Description

This invention relates to the field of flow measurement using ultrasound.

In known ultrasonic flow meters, the oscillations that are received and reflected from the plane of the rigid element arrive at the amplifier, the formation mode of which is limited by the excess signal amplitude above the noise, the amplitude of which for some sensors is comparable to the signal amplitude, which reduces the synchronization of the generator, as well as limits the use of a flow meter to measure flow in a wide temperature range of the measured medium.,

The proposed flow meter is equipped with a time pulse selector included in the synchronous ring between the amplifier-shaper and the pulse generator, waiting, the generator with its input through a pre-amplifier connected to the driver-shaper, and the output through an integrated circuit with the input of the coincidence circuit, the output of which is connected to pulse selector.

This eliminates the effect of a single reflected ultrasonic oscillation.

The drawing shows the proposed flow meter.

The mounts are installed on the bad elements 2 and 3 connected to the switch 4. The switch is controlled by the trigger 5, connected through the block divider 6 to the pulse generator 7.

The other output of the switch 4 is connected to the amplifier-driver 8, one of the outputs of which is connected via a temporary selector 9 to the generator 7, the second output through the pre-amplifier 10 is connected to the standby generator p. The generator output is connected through an integrating circuit with a key 12 to one of the inputs a coincidence circuit 13, the other inputs of which are connected to the triggers of the block of the separator 6, and the output of the coincidence circuit is connected to the temporary selector 9. The switch 4, which switches the bad elements 2n L, allows the direction of the ultrasonic; once in the flow direction and against it. In both cases, the formation of a closed

synchro chain: generator 7 - switch 4 - piezoelectric elements 2, 3 - switch 4 - amplifier-form rover 8 - time selector 9 - generator 7.

A generator of 14 normalized pulses is connected to the output of generator 7, connected through a low-pass filter 15 to amplifiers 16 and 17, the outputs of which are connected to demodulators 18 and 19, respectively, through which the 20 and 21 headers of the splitter unit are connected to the inputs circuits 13. Ultrasonic oscillations in the sensor / are emitted alternately with the flow of the fluid and upstream. Their distribution time is different. If the sound is directed along the flow of a fluid, then the flow velocity of the fluid and the speed of sound in a stationary fluid are summed up; if the ultrasound is directed against the fluid flow, the velocities are subtracted. In the first cycle of operation of the flowmeter, short pulses of electrical oscillations of the generator 7 pass through the electronic switch 4 to piezoelement 2, they are converted into ultrasonic vibrations and propagate at an angle to the direction of movement in sensor 1. Ultrasonic oscillations propagating in the sensor along the flow, they are adopted by the piezoelectric element 3, they are transformed into electrical oscillations and through the switch 4 they enter the amplifier 8, where they are amplified, are formed into video pulses and. through the selector 9 again start the generator 7, which operates in synchronization mode. In the second cycle of operation of the flow meter, the electronic switch 4, controlled by the low-frequency pulses from the splitter unit 6, changes the direction of the ultrasonic oscillations in the sensor to the opposite. In this case, the impulses from the generator 7 pass through the same transformations and the same path, but against the flow of the liquid. The generator 7 starts the shaper 14 producing standard impulses stable in duration n amplitude. These impulses are passed to the filter 15, and the variable component at the output of the filter is a switching frequency, the amplitude of which is proportional to the difference frequency and, consequently, to the flow rate. The variable component is amplified by preamplifiers 16 and 17 and fed to demodulators 18 and 19. Switching demodulators takes place synchronously with the switching frequency of circuits 20 and 21. A constant voltage, proportional to the flow rate, removed from both demodulators is supplied to the input of the indicating device 22. With the amplifier-amplifier 8, successively amplified by the amplifier 10, is supplied to the waiting generator 11, which at the initial moment is triggered by an interference pulse and gives a pulse duration not exceeding barns period repetition frequency of the pulse generator. From the output of the standby generator, pulses are fed to an integrating circuit with a key 12 (delay element) designed to delay the pulses of the waiting generator. The delay time is set taking into account the reliable operation of the selector 9. From the output of the integrating circuit with key 12, the delayed pulses, along with the pulses from all divisions except the last, go to circuit 13, at the output of which a gate pulse is formed, necessary for gating the selector 9. From the output the selector, the signal pulses are sent to the start of the generator 7. Object of the invention: an ultrasonic flow meter containing two acoustic transducers, a switch with a trigger, a divider unit, a generator with an amplifier a pulse generator connected to a synchro-cage circuit and a pulse-frequency modulation detector, characterized in that, in order to eliminate the effect of a once-reflected ultrasonic oscillation, it is equipped with a time selector of pulses included in the sync-ring between the amplifier-shaper and the pulse generator, which is waiting for the generator the input of which is connected via a pre-amplifier to the amplifier-shaper, and the output through an integrating circuit with the input of a coincidence circuit, the output of which is connected to the pulse selector.