SU1619086A1 - Leak detector - Google Patents

Abstract

The invention relates to a test technique and allows for improved accuracy by providing an estimate of the magnitude of the residual background signal. The leak detector 1 contains a control unit 2, an averaging unit 3, shift registers 4-6, an arithmetic unit 7, and a subtraction and display unit 8. The magnitude of the background signal is averaged in averaging block 3, then recorded sequentially by shift registers 4-6. The arithmetic unit 7 calculates and provides the value of the compensation signal to the subtraction and display unit 8 for consideration in preparing the leak detector for operation. 1 il.

Description

J

ABOUT

yoo o

00

about

The invention relates to a test technique and can be used in the engineering, aviation, chemical and other industries.

The purpose of the invention is to improve accuracy by providing an estimate of the magnitude of the residual background signal.

The drawing shows a block diagram of a leak detector.

The leak detector 1 contains a control unit 2, an averaging unit 3, the first input of which is connected to the first output of the control unit 2, and the second - to the output of the leak detector 1, shift registers 4-6, the first inputs of which are connected to the second output of the control unit 2, arithmetic unit 7, the first, second and third inputs of which are respectively connected to the first outputs of shift registers 4-6, and block 8 of the subtraction and indication, the first input of which is connected to the output of the arithmetic unit 7, and the second to the first output of the averaging unit 3, the second output which union of a second input shift register 4, a second output connected to the second input of the shift register 5, a second output connected to the second input 6 of the shift register.

The leak detector works as follows.

Before starting the test, control unit 2 is turned on. The control unit 2 outputs the setup signals to the averaging unit 3 and the registers 4-6 for zeroing them, and then the enable signal to the averaging unit 3. After completion of the averaging, a write signal is applied to the input of the shift registers 4-6. The information from the averaging unit 3 is written sequentially to the shift registers 4-6. After three averages, all registers 4-6 of the shift will be filled.

The arithmetic unit 7, having made the calculation, will give the value of the compensation signal a oo. After each new value of the averaging value of the background signal is obtained, the result of the calculation "oo" will change. If several stable results are obtained, ao of the conditions

a ° V g --1soi.

a. ooi - i

(D

The leak detector 1 is switched to the operation mode. The information in registers 4-6 shift is no longer updated and a constant compensation value is output. The control unit 2 stops issuing write pulses to the shift registers 4-6, and the averaging permission signals continue to flow to the averaging unit 3 until the end of the tests.

The process of gassing a product can be described by an exponential. therefore, the approximating function has the form:

 e

-k t

+ a

00

(2)

00;

..Q where t is time;

and oo is the limit of the function at t

A, k - coefficients. Derivative of the approximating function (2)

15a -kA-e kt. (3)

Taking into account formula (2), function (3) can be written as

20

"K (a oo - a),

(four)

where and is the continuous value of the background.

In practice, the dependence of the background on time in the process of evacuation contains

the random component, therefore, instead of the continuous value “, one should take the discrete values a i, obtained by averaging the true value of the background over a certain time interval Ati. The transition to the final increments and taking At const, from the expression (4) we get

Actj

k (a "-a,

(five)

where Aa (is the change in the background over time At; a is the value of the background at the initial moment. For three consecutive values, you can write

(BUT

40

k (aoo-a2):

(6)

03 02

45

 k (and co - oz).

(7)

Excluding Ati and k, we get

“00

oa - ai Q5

0 | + 03 - 2 “2

(eight)

Expression (8) is the starting point for calculating the compensation value of the background signal.

Claims (1)

Claims of Invention A leak detector comprising a control unit and an averaging unit, the first input of which is connected to the first output of the unit. control, and the second input - with the output of the detector, characterized in that, in order to increase accuracy by providing an estimate of the magnitude of the residual background signal, it is equipped with first, second and third registers, an arithmetic unit and a subtraction and indication unit, the first inputs of the first , the second and third registers are connected to the second output of the control unit, and the first outputs of the first, second and third registers are co0. responsibly with the first, second and third inputs of the arithmetic unit, the output of which is connected to the first input of the subtraction and indication unit, the second input of which is connected to the first output of the averaging unit, the second output of which is connected to the second input of the first register, the second output of which is connected to the second input of the second register, the second output of which is connected to the second input of the third register.