RU1778583C - Low pressure gauge - Google Patents

Abstract

The invention relates to measuring technique and is intended for measuring low pressures in the range (2.0 ... 1X) of 133 Pa in a pressure chamber. The purpose of the invention is to improve the accuracy of measuring the ultra-low pressure of a gas chamber in a pressure chamber. The goal is achieved in that the device comprises a vacuum inlet made in the form of a pipeline consisting of three chambers connected in series, separated by interchangeable diaphragms having calibrated openings, while the first vacuum inlet chamber is connected to the atmosphere through a protective filter, is hermetically closed by an adjustable valve, and connected to an exemplary vacuum gauge, a third chamber is hermetically connected to a pressure chamber in which pressure is measured, and is connected by a pressure tube to a static pressure connection of the sensor Single differential, and the second chamber vakuumvoda enclosed between the first and third chambers, communicating with them through a different aperture section and is connected with a nipple germotrubkoy dynamic pressure differential pressure sensor connected to a voltage regulator connected to the power source. 1 C.p. f-ls, 1 ill. next to

Description

The invention relates to measuring equipment, in particular to vacuum gauges, and can be used. When measuring low pressures in vacuum systems in the measuring range (2.0-1 -) 133 Pa, for example in a pressure chamber.

Devices for measuring low pressures are known, for example, thermoelectric pressure gauges 1. Their disadvantages include the dependence of the pressure gauges on the change in ambient temperature.

Close to the proposed device for measuring low pressures (prototype) is a device containing a camera system, a pressure sensor connected to a stabilized power supply, and an exemplary vacuum gauge 2. Its disadvantage is the relatively low accuracy of pressure measurement.

The purpose of the invention is to increase the accuracy of low-pressure measurement, which, when using the device in pressure chambers, will improve their operational performance when testing high-altitude equipment of aircraft

The goal is achieved in that the device. equipped with a measuring vacuum inlet, made in the form of series-connected first, second and third chambers, the first chamber communicating through a series-connected filter and valve with the atmosphere, the third chamber is equipped with an inlet pipe for connecting to a measured pressure source, and between the first and second chambers , the second and third cameras are equipped with the first and

XI XI

since

00

W

a second calibrated diaphragm, with an exemplary gauge vacuum gauge connected to a two-way pneumatic switch, the first input of which is connected to the first chamber and the second to the second, the differential pressure sensor is connected by its first input to the second chamber, and the second input to the third chamber, while the cross-sectional areas FI and Fa of the first and second calibrated diaphragms are selected by the ratio

Ј2 Rd

FI RB where RA is the pressure in the first chamber;

RB is the pressure in the second chamber, while the valve is made adjustable.

The invention is illustrated in the drawing, which is a functional diagram of a device for measuring vacuum.

The device comprises a differential pressure sensor 1, which is connected to a voltage stabilizer 2 connected to a power supply 3, an exemplary gauge vacuum gauge 4, a vacuum inlet 5 made in the form of a pipeline consisting of three chambers 6-8 connected in series, separated by washers - diaphragms 9 having openings liberated for the required measuring range, wherein the first chamber 6 of the vacuum inlet 5 is connected to the atmosphere through a protective filter 10, is hermetically closed by a valve 11, and connected to an exemplary with an anometric vacuum gauge 4, the third chamber 8 of the vacuum inlet 5 is hermetically connected to the pressure chamber 12 of the high vacuum, in which the pressure is measured, and connected by a pressure tube 13 to the static pressure fitting 14 of the differential pressure sensor 1, and the second chamber 7 of the vacuum inlet 5 is enclosed between the first 6 and third 8 cameras, communicates with them through washers-diaphragms 9 of various sections and is connected by a pressure tube 13 to the fitting 15 of the dynamic pressure of the differential pressure sensor 1. In addition, the valve 11 has a manual mechanism 16 for adjusting the initial pressure in the first chamber 6, and the differential pressure sensor 1 is connected to the indicator 17 and the recorder 18. An exemplary gauge vacuum gauge 4 is connected through the toggle switch 19 to the first, second chambers 6. 7.

Measurement of ultra-low pressures (vacuum) is carried out as follows. Set the pressure measurement range. equal to (2-1) x133 Pa. Then, in accordance with the measured range, we select the differential pressure sensor 1. Before the beginning

measuring the vacuum in the pressure chamber 12 determines the caliber area FZ of the cross-section of the second washer-diaphragm 9, installed between the second 7 and third 8 cameras, in accordance with the expression

with PA Fi F2,

where FI is known, pre-selected, proceeding from the required measurement range,

the cross-sectional area of the opening of the first diaphragm 9 mounted between the first 6 and second 7 cameras;

Rd is the pressure in the first chamber 6; RB pressure in the second chamber 7,

The diaphragm washers 9 of the selected caliber, first and second 9, are installed in the chambers 6.7 of the vacuum inlet 5, thereby the required low pressure measuring range is selected. So that the calibrated washers

9 is not dirty, after valve 11 in the first

6, a cleaning filter 10 is installed. Then, to perform pressure measurements in the pressure chamber 12 using the manual mechanism 16, the valve 11 in the first chamber 6 establishes a stable pressure,

controlled by an exemplary gauge gauge 4 (toggle switch 19 in the left position), while in the second chamber

7 establishes a constant, initial pressure. A gas stream with a critical speed throughout the vacuum path 5 is provided by installing consumable washers-diaphragms 9 with calibrated holes, a given value of the reference pressure in the first chamber 6 and the initial pressure in the chamber 7. Cutoff of the vacuum measurement range (2-1-10) x133 Pa carried out by accelerating the gas jet to a critical speed, which leads to

the fact that a constant gas flow rate is established in the vacuum duct 5, and a constant pressure is established in the second chamber 7, which is controlled by the vacuum gauge 4 when the toggle switch 19 is in the right position. As a result, the pressure of the selected value set in the second chamber 7 is supplied through the pressure tube 13 to the dynamics of the differential pressure sensor 1, and the pressure in the third chamber 8, where the pressure equal to the pressure in the pressure chamber 12 is set, is fixed by the statics of the differential sensor 1. Turning on the power source 3 sensors 1 differential pressure, we continuously monitor the value

measured pressure (vacuum), reading and recording its readings respectively on indicator 17 and recorder 18.

So, by changing the pressure transfer in chambers 7 and 8, we determine the pressure in the high-pressure chamber 12. A further decrease in the pressure in the pressure chamber (after the second calibrated diaphragm 9) has almost no effect on the change in gas flow, and, consequently, on the pressure in the second chamber 7. This makes it possible to detect, with the aid of the differential pressure sensor 1, the pressure change between the second chamber 7 and the pressure chamber 12 (the measurement object) almost linearly, which significantly increases the measurement accuracy.

Claims (2)

The vacuum measuring device can be used to measure and record ultra-low pressures of the gas mixture of the pressure chambers when testing the life support systems of vehicle crews, regardless of the change in ambient temperature and with a significantly smaller measurement error. SUMMARY OF THE INVENTION 1. A low pressure measuring device comprising a differential pressure sensor connected to a stabilized power supply and an exemplary pressure gauge, characterized in that, with the aim of increasing accuracy, it is equipped with a measuring vacuum lead. made in the form of series-connected first, second and third chambers, the first chamber communicating through a series-connected filter and valve with the atmosphere, the third chamber is equipped with an inlet pipe for connecting to the measured pressure source, and between the first and second chambers and the second and third chambers respectively, the first and second calibration diaphragms, and the exemplary gauge vacuum gauge is connected to a two-way pneumatic switch, the first input of which is connected to the first chamber, and the second is with the second, the differential pressure sensor is connected by the first input to the second chamber, and the second input is connected to the third chamber, while the cross-sectional areas FI and F2 of the first and second calibrated diaphragms are selected by the ratio F2 / Fi RA / RB, where RA is the pressure in the first chamber: RB is the pressure in the second chamber. 2. The device pop. 1, characterized in that. that, in order to increase the accuracy of the measurement by providing a critical gas flow in the second chamber, the valve in it is made adjustable.