SU157807A1 - METHOD OF EXCLUSION OF THE INFLUENCE OF PARASITIC - Google Patents

Description

The known methods of eliminating the influence of reflected signals are very complex.

The proposed method allows using simple means to completely clear the working signal of distortions caused by reflected sigpa. scrap.

A measure of the flow rate is the difference between the pulse repetition frequencies sent to the controlled medium along the flow and against the flow of the fluid.

FIG. 1 is a diagram illustrating the method; in fig. 2 shows the time diagrams of the pulses: a - without a delay line, b - with a delay line.

From the generator. (Fig. 1) the electrical impulse arrives at the transducer 2, which converts it into ultrasonic vibrations propagating at a speed C in a stationary medium or at a speed C + V into a motion displacement medium.

Transducer 5 receives these oscillations and transforms them. An electrical signal, from which an impulse is generated in amplifier-limiter 4, starts up again: n generator 1.

No. 157807

Thus, during synchronization, the generator gives pulses of happiness / 1, depending on Cl, i.e., on flow:

, 1 with L c

  77 T

where is the time of its propagation from the transducer 2 to the transducer 3.

I is the distance between 2 to 3 transducers. To create a shift between the operating l of the reflected impulse, a delay line 5 is used.

FIG. 2 Г1,2, з ... - triggering electrical impulses, Л1, о, з ...- working signals, 5i, 2,: 3- .. - reflected signals.

The working signal Ld (Fig. 2a) and the reflected signal B (from the working signal triggered two periods earlier) arrive at the receiving transducer simultaneously.

Similarly, with the signals A. and 8-2, A-, and Bf, etc.

If the time from the start of the generator with the first impulse of the synchronization G to the arrival on the converter 3 of the first reflected signal BI is / ob and the time until the working signal AZ is received through ta, then

/ - 9f- -L f, 4 / - Q / -

01 - 1 T- f--, is - - I

c - {- v with - is + y

where 1 is the time from the start of the first synchronization pulse G to the arrival of the first operating signal Li on the converter 3, and 1 is the time of the passage of the same pulse against the fluid flow.

The time shift A / sa -, where with, i.e.

almost complete coincidence of the working and reflected signals.

Since D / is dependent on c, which varies with temperature, when you change and temperature, the worker will have the powerhrita: will add to reflected in different phases, which leads to a distortion of the shape of the working signal.

To avoid this distortion, the working signals are shifted in time relative to the reflected signals by time 2,, (;), and the delay time of the electrical signal by delay line 5. As a result, the repetition period of the synchronization signals becomes T ti + (;; ad

The signal Lz comes through a period of time

t, 2 (f, -t, ad} + ii The reflected signal L / comes through the time interval

01: 2/1 4 t 1

The time shift between the working and reflected signals (for signals L; / and Bi) is equal to

D # t. -1 ,, 2 (fj +, ““) + t, - (2 /, -f,) A / - It., - h for i: g 2t. “T, - / i, M t ,.

Thus, all the working impulses will be shifted in time by: time, rstvnye, about 2t; dd).

Subject invention

A method for eliminating the influence of parasitic reflections in acoustic circuits, frequency pulse ultrasonic flow meters, characterized in that, in order to eliminate distortion of the operating signal when the reflected signal is superimposed on it, the working signal is temporarily shifted relative to the separated signal via an electric delay line .