SU1221514A1 - Method of testing linearity and calibration characteristic of low pressure gauges - Google Patents

Abstract

The invention relates to instrumentation engineering and allows for improved accuracy and the ability to determine hysteresis. In the course of direct calibration into a tank with a large volume, gas is repeatedly expanded from tank 3 with a significantly smaller volume, which is under known pressure. The pressure in the tank 9 and on the pressure gauge is incremented in 10 equal steps up to the value equal to its measuring range, after which the pressure corresponding to the upper limit of the measurement of the gauge to be tested is established. During the reverse calibration from tank 9, the gas is expanded into tank 11, equal to it in volume, with a lower predetermined pressure. Ensure that the pressure in the reservoir 9 decreases with a calibrated pressure gauge 10 in the same steps as in the forward run. 1 il. Yu GO | YuA O1

Description

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15

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The invention relates to a control-1-measuring technique and is intended to verify the linearity and the expiration of the calibration characteristics of absolute pressure micromanometers.

The aim of the invention is to increase the accuracy and possibility of determining the hysteresis.

The drawing shows a diagram of an apparatus for carrying out the method.

The device contains a gas intake system 1, which is connected via valve 2 to tank 3 with an exemplary pressure gauge 4. Tank system 6 is connected to tank 3 through valve 5, and tank 9 is connected through valves 7 and 8 with a calibrated pressure gauge 10 and volume tank 11.

The tanks 9 and 11 are interconnected through the valve 12, and through the valves 13 and 14 are connected to the pumping system 6.

To increase accuracy, the volume of each

The second of tanks 9 and 11. should significantly exceed the volume of tank 3 (for practical purposes it is enough 100-200 times). Tanks 3, 9 and 11 are equipped with high vacuum indicators that control the residual pressure (not shown).

The verification method is as follows.

In the course of direct calibration to tank 9, gas is repeatedly expanded from tank 3 with an exemplary manometer 4, which is under known calculated pressure, and provides an increment of pressure B; tank 9 and, in a controlled manometer, is equal to 10 steps equal to its range measurements. In this case, the pressures that must be created using the gas inlet system 1 through the valve 2 in the tank 3 are calculated according to the formula 25

thirty

35

40

45

(i)

Fp (i, (1 + od) -. (And

(one)

de P

5 (O

9 (f)

9 (i-h)

pressure created in reservoir 3 to ensure the i-th calibration point; pressure created in reservoir 9 to ensure the i-th calibration point; pressure remaining in tank 9 after the previous one (i-O-th calibration point;

five

0

one

five

0

five

0

five

0

five

51/4 2

UE

L rj is the ratio of the reserves 3 to the volume of the tank 9, i is the graduation point (i

 1p).

For the implementation of the forward course of graduation, the following operations are performed:

1. Calculated by the formula (1) pressure, which must be consistently created in the tank 3.

2. Vacuum using the pumping system 6 through the vacuum valves 5,

The 13 and 14 tanks are 3, 9 and 1 to a residual pressure that is two orders of magnitude less than the lower limit of measurement of the manometer to be tested.

3.Closes taps 5, 13 and 14 with the help of gas inlet system 1 through a valve. .2 in reservoir 3, pressure J is required to obtain the 1 st calibration point. The pressure P (-) is measured by the reference plate 4,

4 „Close valve 2 and open. valve 7. At the same time, in the system, tanks 3), 9 - a rotating pressure gauge 10 creates pressure) corresponding to the 1st point of the calibration characteristic.

5. Repeat the operations of PP, 3, 4 for the Boeh points of the calibration characteristic, for which the pressures defined in section 1 are used.

After the pressure P in the tank 9 is created, which corresponds to the upper limit of measurement of the manometer 10 being tested, the graduation flow is completed, and the tank 9 is disconnected from the tank 3 by valve 7. 11 with a lower predetermined pressure P, and thus provide for a decrease in pressure in reservoir 9 with an adjustable manometer 10 such steps as during the direct course of calibration.

To perform the reverse calibration, the following operations are performed.

 1. Calculate the pressure that must be created in the tank 115 according to the formula

p 9r - p:

(2)

2. Calculate the pressure P

l (} which must be created in the reserve

voire 3, according to the formula

 es about

Pm;) Vq - “- Y).,

 and I

V

 R.

S

3

(((5) 1 + s,

lapping

3. using system 1

gas with an open valve 2 create a pressure in reservoir 3 .-- il

4. The valve 2 is closed, the valve 8 is opened. At the same time, in the tank 11, a pressure P is established (,

5. The valve 8 is closed, the valve 12 is opened. At the same time, the pressure in the system of tanks 9, 11 is set to hSm-P, the pressure gauge being calibrated, the pressure corresponding to the (n-1) -th point of the calibration characteristic is given during the return stroke.

6. The valve 12 is closed, the valve 14 is opened and the tank 11 is pumped out, after which the valve 14 is closed.

7. Repeat the operations according to claims 3-6 for each point of the calibration characteristic, thereby performing the reverse course of calibration.

Compared with the known method, the invention allows the creation of pressure increments in equal steps in the forward and reverse steps of the calibration, which allows to determine

Editor M. KelemeSh Order 1603/47

Compiled by And, Nevsky

Tehred Oh, GorTVi Proofreader. Ferenc

Circulation 778 Subscription VNIIPI USSR State Committee

on inventions and discoveries 1130355 Moscow, Zh-35, ° Rautska nab. 4/5

Filial PPP Patent 5 g, Uzhgorod, st. Project, 4

3)

m

22151

hysteresis and increase the accuracy of the linearity of the calibration characteristics of gauges.

Claims (1)

Invention Formula The method of checking the linearity of the calibration characteristics of low-pressure gauges by pre-evacuating the system from two tanks of different volume, supplying pressures to the tank of a smaller volume up to. the upper limit of the monitored pressure gauge and the measurement of pressure in the thread after the tanks are connected to each other, characterized in that, in order to increase accuracy and the possibility of determining hysteresis, in the direct course, the pressure of the gas in the smaller volume of the tank will be reduced in steps, controlling them with an exemplary manometer, after steps, trans. repusk gas into a larger tank with a controlled pressure gauge, getting 25 there are equal increments of pressure over the entire operating range and, in the reverse direction, in a tank with a controlled manometer, the gas pressure is repeatedly lowered in the same steps, bypassing its portions into a third tank of equal size in it for each stage the initial pressure. 20 .thirty