SU1462131A2 - Method of graduating vacuum gauges - Google Patents

Abstract

The invention relates to a measurement technique, in particular, to the calibration of vacuum gauges. The aim of the invention is to increase accuracy. Model 2 and calibrated 3 vacuum gauges are connected to chamber 1, and the working range of the first is wider than the second. After pumping out of chamber 1, a continuous gas flow is applied with valve 6 closed with valve 6. At certain points in time, starting with t {, vacuum gauge 3 is recorded, and at the final time point it is recorded and read: vacuum gauge 2. After pumping, close again valve 6 and serves in the chamber 1, the gas flow, but significantly less than in the first case. At certain time intervals, the readings of the vacuum gauge 3 are also recorded until a final pressure equal to the pressure at time tj is reached. After pumping back to the chamber, the initial gas flow is again supplied by means of valve 6 to control pumping speed S, at which a constant pressure in chamber 1 is maintained equal to the final pressure in the first case. By measuring the gas flow through the nozzle 4, the chamber 1 is pumped out at a constant rate of S, fixing the readings of the vacuum gauge 3 and -frame when the hits are the same as when fed into the chamber, after which the pressure values are calculated 3. 1 Il. C / s

Description

j The invention relates to emulsion | technology and can be used to determine the metrological characteristics of vacuum gauges, as well as partial pressure meters, and is an improvement of the invention according to the author. No. 808889.

The purpose of the invention is to increase precision.

i The drawing shows a diagram of a vacuum system that implements the proposed method of calibration vacuum-FJOB.

; The vacuum system includes a chamber - Р | У 1 with attached sample vacuum gauge 2 and graduated; Energy meter 3, and the operating ranges of these instruments do not match: an exemplary instrument measures higher pressures than the calibrated one. The gas inlet 4 to the chamber 1 serves as a leak valve 4, and for pumping it out - into the vacuum pump 5. The discharge valve and its complete shutoff are controlled by an adjustable valve 6.

The proposed method consists of the following sequence of operations.

After pre-evacuation of the chamber 1 with the help of an ejector 4, Some constant gas flow Q is fed into it (valve 6 is closed). At the same time, the pressure P, in chamber 1, increases with time t according to:

R. -§- (t, - t,), (1)

In particular,

: - G-b. E (2a)

()

At the final moment of time t, the reading P of the reference vacuum gauge 2 is directly measured.

Regulate the gas flow through the leak 4 to the value Q.iQ and after re-pumping the chamber 1 serves this flow QJ into it (with the valve 6 closed). P pressure in it increases

with time t according to dependencies:

 -Q

 (t v 2.

 (3)

where q is a side stream of sorption and desorption of gases on the walls of the chamber.

Obviously

P, “P,

(four)

At certain times t of the measured time interval t,

i, (.)

fic

calibrate the readings of the calibrated vacuum gauge 3. The moment of time is recorded when the calibrated gauge readings are completely consistent.

g, ().

t;

with the proof of it - P,

Then

in the moment

Where V is the volume of the camera 1;

tf is the starting time.

At certain moments of the measured time interval, the readings of the calibrated gauge 3 are recorded. For the initial and final

moments of time t.:.and t, respectively} are the pressures and are equal to:

and

(sixteen)

(2)

Again, with the help of fluid 4, gas flow Q is fed into chamber 1. Valve 6 controls pumping speed S of chamber 1 to such a value (much lower pumping speed of pump 5 and therefore independent of pressure in the chamber), at which equilibrium is established between inlet and pumping gas in the chamber and kept constant reading. P model vacuum gauge 2. Then

Q. spr

From here s q,

and taking into account equation (16):

S

Shut off the gas supply through the inlet 4, i.e. Closing it, and leaving valve 6 in the same position, pump out chamber 1 at a constant rate of S. During a decrease in pressure, P in chamber 1 is fixed, starting with a reading of P, calibrated with a vacuum gauge 3, times t - t, through which the readings will be the same - in the interval P -, as with the gas supply to the chamber.

The pumping equation has

type: S, c, ni - V - o)

R. R. e

a z

  G - (,

- | -, - e- particular, p; - p g.

,,

(8) 30

(8a)

,

In view of equation (7A):

.-B

-3- (t; - t,) l (9)

with substitution (5):

P p (.,

2 1 t7- t "

{Gt-o fc r -t

- (; t J + e

kc with,

(10) 5 The joint solution of equations (5a) and (10) gives;

ten

„(“), () Ti - to

h 1 yyyyy-1-g- -o

e

/ s f

V-LO t

(-, L- /.

 (t1)

1C {- - / 4- 4- M h p 15 (t -h) It.- -1, I p-e

; - (I {I., k (

Consequently, the S gramping of a vacuum gauge reduces to observing the temporal dependencies of its indications to periodically adjusting the gas flow being pumped and being pumped out and to measuring the pressure once by an exemplary vacuum gauge. The main advantage of the proposed method is the elimination of errors caused by side outgassing and gas absorption streams from the design formulas for the desired pressure.

Claims (1)

Invention Formula Method of calibration of vacuum meters on the author. St. No. 808889J I distinguish ™, and so that in order to improve calibration accuracy, the initial flow of gas into the chamber is again established and, by adjusting the evacuation rate so that the chamber maintains a constant pressure within the measuring range model vacuum gauge 5 record this pressure value, then shut off the gas supply and, continuing pumping out, record over time the same readings as 6bUTii recorded in the first stages of calibration, and calculate the adjusted pressure values, readout raduiruemogo gauge. 0 five