SU885896A1 - Flow mark recorder - Google Patents

Description

(54) FLOW RECORDER RECORDER

one

The invention relates to a measurement technique, and can be used in devices for measuring motion parameters, in particular, the magnitude and direction of the gas or liquid flow rate, flow rate, as well as in aerial and hydrodynamic studies.

Devices are known for contactless measurement of flow rate, velocity, and direction of flow of liquid and gas, the basis of which is based on determining the time of transfer of a label by the flow between points of the base distance. One of the main components that determine the measurement accuracy in such devices is the tag recorder, which binds the signal to the measuring circuit at the time when the mark crosses the boundary of the base distance. The registration of tags in known devices takes place at the moment when the receiver starts responding to the appearance of the tag, i.e. at the time when the receiver signal exceeds a predetermined threshold level.

The main disadvantage of this registration is the inconsistency of the spatial position of the label.

and the receiver output level due to the possible instability of the parameters of the generated tags. Also known are devices in which the registration of a label is provided. in terms of the average point in time - between the beginning and the end of the receiver’s response to the passing label. These devices are also inherent

On the error due to the time dependence of the characteristic parameters of the label. These errors are especially significant at low speeds of the measured flows, when the time interval between the beginning and the end of the response is relatively large.

There are known devices for registering tags by the maximum output signal of the receiver or by the zero value of the derivative of this signal with respect to time 2.

A disadvantage of the known devices is their low accuracy.

25 The closest to the present invention is a tag recorder, containing dotted electrodes along the stream, an amplifier, a differential circuit connected to

30 comparator In this case, the electrodes are placed at a distance of 0, b6 of the length of the marks. In this device, a differential circuit is used to separate the difference signal between the time-spaced output pulses of receivers spaced apart. Next, a comparator is used to generate pulses, the temporary position of the leading edge of which corresponds to the instant of crossing the difference signal through the zero level of the GB.

However, this device also does not provide high accuracy of tag registration in the presence of signal fluctuations At the input of the comparator, which take place in actual work conditions (flow turbulence, random pulsations, etc.). At the same time, the registration error is caused by the small steepness of the crossing of the zero difference signal, especially at low speeds of the controlled flow. In addition, the selection of the receiver spacing along a stream of 0.66 tag lengths for a number of tag types is not optimal c. points of view to ensure high accuracy of recording, and, consequently, measurement of motion parameters.

The purpose of the present is to improve the accuracy of tag registration.

The goal is achieved by the fact that, in the flow tag recorder, there are dotted electrodes along the stream, amplifiers and a differential circuit connected to a comparator, and a second differential circuit connected to a comparator, while the electrodes are connected to different polarity input circuits and located on distance L Y yr, where Gd is the shortest distance between the trajectory of the mark and the line connecting the electrodes.

The introduction of an additional differential circuit and the indicated inclusion of it allow the formation of a so-called comparator reference signal, changing in antiphase to the main signal. Due to this, the steepness of the intersection of the main signal with the reference signal is doubled, which, due to a decrease in the variance of the time error, leads to an increase in the accuracy of the registration of tags under conditions of random pulsations and turbulence of the measured flow. The choice of the distance of receivers according to the specified expression when registering tags with electrostatic charge ensures the maximum slope of the signals at the output of the receivers in the equisignal zone, which also increases the slope of the difference

signal and improves register accuracy.

FIG. 1 shows a registrar circuit; in fig. 2 - time diagrams that show his work.

The recorder contains two identical receivers 1 and 2 spaced apart, consisting of recording metal electrodes located on the surface limiting the flow to be monitored, and charge-voltage converters whose inputs are connected to the said electrodes. The outputs of receivers 1 and 2 are connected via two differential circuits 3 and 4 with a comparator 5.

The registrar works as follows.

The ion tag, as a result of its movement, together with the controlled flow passes first around receiver 1, and then around receiver 2. As a result, signals 5-1 and Sj appear at the output of receivers 1 and 2, respectively. These signals are fed to the corresponding inputs of the differential circuits 3 and 4, at the output of which the signals aS and dScL are generated corresponding to the differences (S, and the signal d5 (inverse to the signal d5. From the outputs of circuits 3 and 4, the signals d5 and & Sij is fed to the corresponding inputs of the comparator 5, in which the pulse is generated at the moment of equality of the signals d, 5 and d S / j, and the difference signal is equal to d5 - (-d5) 2uS, i.e., increases by 2 times. the position of the leading edge of the pulse at the output of the comparator corresponds to the moment Tagged the passage points equidistant from the receiving electrodes. This pulse is used in the measuring circuit for determining the transit time Tagged predetermined reference distance.

As a result of the passage of the mark near the point metallic electrode, charge q occurs on the latter, due to the induced charge. The magnitude of the induced charge q made from known curvature

Yan Hm where -H is the potential of the fictitious floor

point electrode at the point where the mark is located. Differentiating this relationship over time, we obtain an expression describing the induced current pulse

    cosfb,

where V is the speed of movement of the mark;

G - is the shortest distance between the electrode and the trajectory of the tag;

I is the angle between the tag's trajectory and the radius of the vector connecting the tag to the electrode. Extreme values of i, corresponding to the maximum steepness of the change in charge, occur at angles that are from the condition df / dt 0. As a result of solving this equation, we get tg (b Y2 t, e. | 1 (, t - 54 44, 0 opg 126 ° 16. The distance between the electrode and the projection of the mark on the plane of the electrodes, when the induced signal is at a maximum slope, is defined as (Fig. 1). Obviously, if the receivers are located at a distance of 21 d L from each other, then the induced signals on them will intersect at the point having the maximum Therefore, it is possible to determine the optimal size of the separation of the receiving electrodes. Since for the point electrodes tg, V7, then .ETO-distance. is determined by the height of the mark Gd and is equal to H 2g, / V YTG In the General Case which achieves the greatest slope of the Jats signal, depends on the geometry of the receiver electrode and can be calculated for a specific case.

at

fienmt. g. Thus, placing two identical receivers at a specified distance and introducing an additional differential differential can significantly increase the accuracy of tag registration. invention of the invention of the flow tag recorder containing point electrodes, located along the stream, amplifiers, a differential circuit connected to a comparator, distinguished by the fact that, in order to improve accuracy, a second differential circuit was inserted connected to a comparator, while the electrodes connected to different polarity input differential circuits and located at a distance L –UR g, where rj is our shortest distance between the trajectory of the mark and the line connecting the electrodes. Sources of information taken into account in the examination 1. Kremlevsky ETC. Flow meters and quantity counters. L., Mechanical Engineering, 1975, p. 577-578. 2. In the same place 588-591. .. 3. Authors certificate of the USSR № 657352, cl. G 01 P 5/18, 1979 (prototype) ,.

t

Claims (1)

SUMMARY OF THE INVENTION A flow mark recorder comprising point electrodes, located along a flow, amplifiers, di. The differential circuit connected to the comparator is distinguished by the fact that, in order to improve accuracy, a second differential circuit connected to the comparator is introduced into it; herewith, the electrodes are connected to bipolar inputs of the differential circuits and are located at a distance .. B th, where r ₅ is the shortest distance between the trajectory of the mark and the line connecting the electrodes.