RU24287U1 - LOAD MANOMETER - Google Patents

Description

The utility model relates to the field of pressure measurement: in particular, verification and calibration of pressure measuring instruments.

Widely known are 1 deadweight piston manometers (GPMs) that reproduce pressures with high accuracy in a wide pressure range, while liquid or gas are used as the medium transmitting the pressure. Known GPMs (Fig. 1) consist of a support base 1, a cylinder 2 fixed thereon, a piston 3, which makes up a piston pair with a cylinder with a gap of not more than a few micrometers, and loads (loads) 4 on the piston. Between the piston and the cylinder is a working fluid 5, which acts as a lubricant. During operation, the piston rotates continuously due to the inertia of the loads or from a special rotation drive, which creates a viscous wedge that centers the piston in the cylinder, so that only fluid friction exists between them and there is no dry friction. Under the influence of reproducible overpressure, liquid from the HIM flows out through the gap of the piston pair, due to which the piston lowers, replacing the volume of the outgoing liquid. GPM reproduce pressure in accordance with its physical definition: the pressure under the piston is equal to the gravity of the piston with the loads, divided by

effective area of the piston pair (arithmetic mean of the cross-sectional area of the piston and the cylinder bore). These instruments are the material basis of the system for ensuring the correct measurement of pressure in all countries, both at the level of state standards and working standards, which are used to verify and calibrate working pressure measuring instruments. When performing calibrations or calibrations, the pressure at the inlet of the calibrated means is equal to the sum of the pressure under the piston of the PMG and the pressure of the hydrostatic column of the medium transmitting the pressure between the piston and the inlet of the calibrated means. Thus, due to the lowering of the piston, the pressure at the inlet of the calibrated measuring instrument continuously changes. When reproducing small pressures, this change is significant, which is a disadvantage of traditional GPMs.

Gas-fueled gas-powered gas mills are deprived of this drawback, since the gas density is hundreds of times less than the density of liquids and, accordingly, the pressure of the column of the medium transmitting the pressure between the piston and the calibrated pressure measuring device is as much less. However, to ensure the operability of such PMFs, the clearance in the piston pair should be ten times smaller, that is, not exceed tenths of a micrometer, since the viscosity of the gas is also hundreds of times lower than that of the liquid. Because of this, the cost of manufacturing such PMFs is much higher, and the operation is much more difficult, since it requires special measures to filter gas from particles with a size of the same tenths and hundredths of a micrometer.

Thus, there is a contradiction: to reduce the error, the GPM must run on gas, and to reduce its cost, on liquids. The proposed utility model solves the contradiction and makes it possible to reproduce low pressures with deadweight pressure gauges without loss of accuracy due to the uncertainty of the height of the hydrostatic column between the end face of the PMM piston and the input of the pressure measuring instrument being verified.

This technical result is achieved due to the fact that in the proposed PMU containing the base, loads, cylinder and piston, the last two dimensions are opposite to the standard GPM: the piston is located below, on the base (on which the cylinder is usually located), and through the hole in the piston pressure is supplied to the piston pair, and the cylinder is located on top and carries the load (in a conventional gasoline piston, the piston carries the load). The upper slice of the hole in the piston is located above the end of the piston. A piston is filled with liquid, which, under the action of gravity, itself enters the gap between the piston and the cylinder, while the pressure between the bottom of the cylinder is perceived; there is always gas (for example, air) between the bottom of the cylinder and the device being checked, due to which the column height of this gas changes, caused by the inevitable mixing of the cylinder in height during the operation of the PMG, does not significantly affect the reproducible pressure.

The device and operation of the proposed GPM is illustrated by the drawing shown in FIG. 2.

The GPM contains a piston 1 located on a support base 2, a cylinder 3, and weights 4 hung on a cylinder. The fluid on the piston is indicated by the number 5. Under the action of gravity and excess pressure under the cylinder, the fluid enters the gap between the piston and the cylinder, forming a hydraulic lock and centering; its viscous wedge due to continuous flashing; cylinder rotation (by inertia or by force rotation drive) . The working medium that transfers pressure to the calibrated measuring instrument, gas (air), is fed into the space under the cylinder above the liquid, so that the liquid does not enter the pneumatic system, that is, the gas pressure transmission system.

low pressures without a significant increase in the cost of verification (calibration)

Sources of information

1. Gramenitsky V.N. Piston measuring instruments. -M .: Publishing house of standards, 1973.

Claims (1)

A deadweight tester with a support base, weights, a piston pair consisting of a piston and a cylinder, and a fluid in the cavity between the piston and the cylinder, characterized in that a piston is located on the support base, a cylinder carrying loads is placed on top of it, the piston is made with a channel for supplying a working gaseous medium under the cylinder, and this channel ends above the end of the piston and the liquid forming a hydraulic shutter in the gap of the piston pair.