SU395724A1 - SINGLE-CHANNEL ULTRASONIC FLOWMETER - Google Patents

Description

one

The invention concerns flow using ultrasound.

In the known single-drop ultrasonic flowmeters, the quantization of the time intervals of pulses with a frequency rate proportional to the speed of ultrasound is not completely eliminated, the dependence of the output signal on the speed of ultrasound in the measured medium is not completely excluded.

In the proposed device for precision measurement, the measuring device is designed as a stable frequency generator, connected to the mixer input, to another input of which a generator is connected, and the outputs are connected to the input nI of the mixers, the other inputs are connected to the outputs of the respective single frequency switches, and to the inputs of frequency multipliers The outputs of which are connected to the inputs of the respective mixers, the other inputs of which are connected to the frequency multiplier of the stable frequency generator, and the outputs to the inputs of the Schmit trigger one with differentiating chains, the outputs of which are connected to the inputs of a digital meter of time intervals.

The measuring device contains an expander of time intervals between pulses L, horizontal or liquid flow rate, a digital meter of extended time intervals and eliminates the dependence of the output signal of the flow meter on the ultrasound speed in the measured fluid flow due to frequency conversion from (ultrasonic velocity of ultrasound C). time L to a stable frequency (.) n due to quantization in a digital meter and time intervals by pulses with the following frequency kF, iipo; nd speed of ultrasound S.

The drawing is a diagram of the proposed device.

Flowmeter contains acoustical converter / with four bad elements

9-.

pulsed gee, impulse amplifier

nerator /, selective amplifiers imuls 8 and 9, single vibrator Yu, 11 and measuring device containing mixers 12-16, generator of stable frequency 17, frequency multipliers 18-21, Schmptt triggers with differentiating chains 22 p 23, digital time interval meter 24.

Single impulses from the heater 7 of the single displacement) are fed to the bad elements 2, 3 and 5 and 5 are also fed to the selective amplifiers 8 and 9 to lock them away during the pulse emitting time. The period T of sending pulses and zozoelemites back to the proportional to the velocity C of ultrasound in a fluid and current is determined by the well-known scheme of this rokolc formed by the radiating piezoelectric element 5, the flow, the receiving element and the elec- , СF where D is the distance between the radiating unit 5 and the receiving 4 environmental elements, equal to the diameter of the tube of the converter. The pulses emitted by the piezoelectric element 2 but the flow and the piezoelectric element 3 against the flow, respectively, arrive at the 3 3 2 negative elements through time D t ,,. , (2) sin. (C -J-V cos.) D sin a (C-V COS 2) where a is the angle of radiation; V is the average flow rate. The received piezoelectric elements 3 and 2 imiuls are amplified by corresponding selective amplifiers 9 8 and are fed to start one-shot vibrators // and 10. The latter produce short impulses of duration 1 T, and each pulse from the odiovibrator // advances the emulsion from the single vibrator 10 by time D /, equal to the time difference, and /, V, i.e. 2 Dctff X & ft ,. - t.,. V.. (4) C -WJcOS a Since C2, a member, is denied in the denominator of expression (4), then From expression (5) it can be seen that the online: tolled the D / melade by one-shot pulses W to 11 directly proportional to the average flow rate V and so proportional to the flow rate. The presence in expression (5) of the denominator C determines the measurement error due to variations in the velocity of ultrasound C. The pulses from single vibrators 10 and // are fed to the measuring device. The measuring device expands the interval At between the pulses of one-shot 10 and // by (-J-1) times, eliminates the dependence of the output signal on the ultrasound speed C; Measures with a digital isomer extended and iteration time. The measuring device works as follows. The generator 17 generates harmonic oscillations with a circular frequency ω. Harmonic oscillations from generator 17 are fed to mixer 14 and frequency multiplier 20. Mixers M are also combined with emulsions from the geyoretor 7, the circular frequency of the first harmonic is 2l / -. C. Mixer 14 allocates a co-f co. From the output of the mixer 14, harmonic oscillations w + too / are fed to mixers 12 and 13. Mixers 12 and 13 also receive periodic pulse sequences, respectively, from single vibrators 10 and //, the frequency of which is equal to F. The first harmonics of these periodic pulse sequences applied to mixers 12 and 13 (and the initial phase of the oscillations coming from the generator 10 to the mixer 12 equal to 0) are equal respectively (O / and (O (/ + D /). Mixers 12 and 13 separate the frequency differences of the harmonized oscillations. from which x, respectively (equal), nodayutsya (OO / and 10o (/ + on frequency multipliers 18 19. The latter multiply (+ +) times the frequency iodized by their oscillations. From the outputs of the frequency multipliers 19 harmonic oscillations equal to vectors (n +) (Oo / and (n + l) ((i + nodayutsya to mixers / 5 and 16. Mixers 15 and 16 also add harmonic oscillations / coo / c frequency multiplier b, multiplying n times the frequency of harmonic oscillations of the generator 17. Mixers 15 and 16 allocate the difference frequency of oscillations supplied to their inputs. From the outputs of mixers / 5 and 6 harmonic oscillations. corresponding to equal Mai and (/: J- 1) 0) 0 (/ +). The inputs are supplied to Schmitt flip-flops with differentiation of lepochechki 22 and 23. Triggers are triggered at the time of the zero phase supplied to their input harmonic oscillations. Right-angle pulses from Schmt-Itta triggers, shifted relative to one another by the time interval A / (rt + 1) .t, are differentiated by differentiating chains and iodized to a digital meter of time intervals 24. From the output of a Schmitt trigger with differentiating price 23, it hits a digital meter time intervals 24 start pulse, from the output of the trigger with a differentiating chain 22 - stop-pulse. Quantized kF pulses, proportional to the ultrasound speed C, are fed to a digital time interval meter 24 from frequency multiplier 21, multiplying by k times the frequency of the non-periodic signal F received from the pulse generator 7. The number of nm pulses measured by a digital time meter counter 24 N At / fef, (n + 1) L. one . As can be seen from expression (8), the input signal of the digital time interval meter 24 is directly proportional to the average flow velocity v and. does not depend on the speed of ultrasound C. Fluid consumption is equal to the product of the average flow velocity and the cross-sectional area of the transducer. Subject and problem of ip etep and a single-drop ultrasonic flow meter containing an acoustic transducer, a amplifier, a generator, two selective amplifiers, two single-choppers, a frequency multiplier and a measuring device, characterized in that, in order to improve accuracy, the measuring device is made as a stable frequency generator connected to the mixer input, to another input of which a generator is connected, and the outputs are connected to the inputs of the mixers, the other inputs of which are connected to the outputs of the corresponding Ator, and outputs - to the inputs of frequency multipliers, the outputs of which are connected to the inputs of respective mixers, the other inputs of which are connected to a multiplier oscillator of stable frequency, and outputs - to the inputs of Schmitt triggers with the differentiating circuit, the outputs of which are connected to the inputs of a digital time-interval meter.