SU436253A1 - METHOD OF DYNAMIC GRIDING OF LOW PRESSURE MONOMETERS - Google Patents

Description

The invention relates to the field of instrumentation and can be used to determine the metrological characteristics of operating pressure gauges.

A known method of dynamic calibration of low-pressure manometers is based on the calculated decrease (reduction) in pressure occurring during the molecular flow of gas through apertures (or tubes) of known conductivity.

The disadvantage of this method is the difficulty of performing calibration, which is associated both with adjusting the intake valve to establish different values of the initial pressure PI, and with the need to measure this pressure for each experimental point.

To simplify the graduation process, the proposed method records (or records) the readings of a calibrated gauge for a certain period of time, then measure higher pressure associated with a known relationship with pressure in the calibration chamber, exemplary gauge and compared the time interval corresponding to the measured pressure, with intervals of time corresponding to the process of recording the readings of a calibrated gauge, determine the pressure in the calibration second chamber of the known dependence m.

A vacuum system that implements the proposed method for calibrating low pressure gauges is shown in the drawing. The high vacuum pump 1 is connected to a high vacuum chamber 2. This chamber is connected through a diaphragm 3 of known conductivity and to a calibration chamber 4, which on the other hand is connected through a diaphragm 5 of also known conductivity f / j to a chamber of initial pressure 6. To the initial pressure chamber model pressure gauge 7 and clamping 8. Graduable pressure gauge (or pressure gauge) 9 is attached to the chamber 4.

The method consists (with steady-state molecular flow of gas and equal chambers temperatures and provided that the pressure in the high vacuum chamber is much lower than the pressure in the calibration chamber) from the following operations.

1. After preliminary pumping of the system in the chamber of the initial pressure 6, some pressure PI, O is established with the help of an inlet 8.

2. The signals of the calibrated manometer 9 are counted in time, without the control and measurement of pressure in the chamber of the initial pressure being made at the same time. The pressure in this chamber increases linearly (with

provided that the pressure of the calibration gas at the entrance to the leak detector Rd is much higher than the pressure PI and remains constant) and at time t is equal to: Pr AO + (f-fo), where P, d is the pressure in the initial pressure chamber the time moment 0, Vi is the volume of the chamber of the initial pressure, ON is the conductivity of the natekate 8 in the established position. 3. After some measured period of time, the pressure in the chamber of the initial pressure 6 is measured directly by an exemplary manometer 7. This pressure Pi, k is equal to: (4 -,). Pl.ft Pl, 0 + At PI ,, Pi, k, the pressure PI that corresponds to any time t (t 4) can be calculated based on the known value Pi.k:; (P.5A.ORg Pl.k By substituting expression (3) into the equation) - P - PI, we obtain the dependence of pressure P in the calibration chamber on time t: P JlLp ,, t: il and tk-i. 4. Comparison of these calculated values of pressure P with the corresponding signals of a calibrated manometer 9. For example, the pressure in the chambers should increase within 2-3 hours with the described method of calibration by 2-3 times the value -40 or pressure. Thus, by measuring the relatively high pressure P, k at the end of the calibration process, it is possible to calculate the very low pressure P reproduced 2–3 hours before that by the equation (4). It is necessary only that the calibration time V be much smaller than the ratio - ( In the prospective case, the computational equation (4) will require additional corrections). 50 For the practical implementation of the method / 3) 25 30 it is also required that the conditions PA and P are constantly observed. If the pressure Poison is not constant, but is itself a linear function of time, then under similar conditions of pressure in the calibration and initial pressure chambers are calculated according to the formulas: () (() Then within 2-3 hours it is possible to cover at least four orders of magnitude of the pressure. Eliminating the need to control and directly measure the initial pressure PI for each experimental point makes it possible to simplify the process of , reduced to observing the time dependence of the signals of a calibrated manometer and a single measurement of pressure I. Subject of the Invention A method for dynamically calibrating low pressure manometers by calculating the pressure decrease in the calibration chamber occurring during a molecular flow of gas through an orifice of known conductivity using a standard manometer whose working range is in the area of higher pressures than the calibrated one, characterized in that, in order to simplify the process, measurements, record (or record) the readings of the calibrated manometer for a certain period of time, then measure the higher pressure associated with a known relationship with the pressure in the calibration chamber and, compared the time interval corresponding to the measured pressure, with the intervals corresponding to the registration process the readings of the calibrated m. anometer, the pressure in the calibration chamber is determined from known dependencies.