Overview wiring diagram of laboratory instruments for measuring pressure and diluted

Abstract

Annotation. The theoretical foundations of knowledge of the laws of equilibrium and motion of fluids in relation circuits connecting laboratory instruments and methods of measurement parameters pressure and dilution of liquids and gases at rest and in motion

Keywords: equilibrium and motion of fluids, laboratory equipment, parameters, pressure, vacuum

Hydraulics as engineering science, is studying the laws of balance, movement and interaction of liquids with solids that perebuva¬yut at rest or motion.
       Measurement of pressure or dilution is to set these values in a liquid or gaseous medium. It is necessary for process control and safety production. In addition, this option is used for indirect measurements of other process parameters: level, flow, temperature, density and so on.

Therefore, quantitative determination of parameters of pressure and vacuum in the hydraulic systems is one of the main tasks of hydrodynamics and is an urgent task.

The purpose of the work. Research circuits connecting laboratory instruments for pressure and vacuum in hydraulic systems.

Materials and methods of research. Schemes of installing and methods of measurement parameters pressure and dilution of liquids and gases at rest and in motion, purpose, structure and operating principle of various devices.

Results. SI unit of pressure - Pascal 1 Pa = 1 N / m2. Allowed to use the unit as1 kg / cm2 = 1 atm = 98066.5 Pa;1 mm. Hg. Art. = 133.3 Pa;1 kg / m2 =1 mm. water. Art. = 9,81 Pa etc. Atmospheric (barometric) pressure - a pressure air column. Physical atmosphere of 1 atm = 101 325 Pa =760 mm. Hg. Art. =10.33 m. Of water. Art. ≈ 0,1 MPa. In relation to the physical atmosphere of determined pressure absolute, excessive (gauge), depression (vacuum).

                                                                          (1)

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Instruments for measuring pressure classified:

• the type of pressure measurement:

1) atmospheric - barometers;

2) the difference between absolute and atmospheric pressure
(Overpressure or vacuum) - Pressure and vacuum gauges;
3) excessive pressure difference between points or dilution - differential pressure gauges;

• the principle of action:

1), liquid (water, mercury, alcohol) - measured pressure equalized pressure liquid column;
2) mechanical (spring, membrane) - deformation of the elastic element (hollow tube membrane) according to Hooke's law is proportional to the measured pressure;
3) electric - under pressure sensing element electrical signal is produced;
4) Conventional cargo - pressure, measured gravity of the piston comes up, loaded weights;
5) combined, and others.

Schemes of connection and measuring parameters of liquids and gases at rest and in motion submitted to ryunku 1. To determine small excessive pressure drop liquids (up to 0.03 MPa) used piezometer characterized prosto¬toyu, nahlyadnistyu measurements and high accuracy. The value of overpressure is proportional to the height of liquid in the vertically installed and the atmosphere vidkry¬tiy glass tube, Pa:

                             ,                                                              (3)

where ρ - density of the liquid, kg / m3;

g - acceleration of gravity, m / s2;

hp - piezometric height, m.

Excessive pressure (vacuum) gaseous fluids vyzna¬chaty comfortable U-shaped manovakuumetrom for the difference in liquid level gauge tubes. In addition to gauge pressure measured it ve¬lychyna vacuum, Pa:

                             ,                                                      (4)

where h_в - height vakuumetrychna city.

When replacing one of the U-tubes manovakuumetra cup reduced relative measurement error. This led vykorysta¬nnya such manovakuumetriv in cases requiring high accuracy pressure or excessive dilution. Increased sensitivity, and hence measurement accuracy can be achieved tilt measuring tube with a scale at an acute angle to the horizontal. This is typical micromanometer that allow along with high accuracy to measure small quantities of excessive pressure and vacuum (1000 Pa). Thus using the formula:

                               ,                                              (5)

where L - counting, on a scale micromanometer, m;

α - angle of vymiryu¬valnoyi tube hail;

C - constant, given in pas¬porti micromanometer.

Tyahomiry the principle of action is different from micromanometer not have a fixed angle of inclination to the horizon. Both are usually filled with ethanol to obtain a clearer meniscus in the measuring tube, with a low density of alcohol increases toch¬nist measurement.

Great excessive pressure (100 MPa) measured ma¬nometramy spring. Under the pressure of a hollow tube-spring is deformed and moves the arrow, fixing the value of this pressure on the scale. Analo¬hichno arranged diaphragm gauge that measures pressure to 3 MPa. The deformation of the membrane is transferred to the arrow that shows the pressure measured.
The same design should vakuumetry that measure the pressure to atmospheric low. Manovakuumetry measure positive and negative overpressure. Zero manovakuumetra scale corresponds to atmospheric pressure.

Recently obtained distribution vantazhoporshnovi gauges. High precision measurements led to their use as a model for all devices in the range of 10-1 - 1013 Pa.
To measure the pressure difference between two points vykorystovuyut¬sya differential pressure gauges, U-shaped tube manometer dzvonykovyy.

Pressure drop is determined on a scale devices prohraduyovanu Pascal, or the formula:

                                                   ,                                                     (6)

where h - indications manometer city.

         Depending on how you connect the differential pressure gauges mo¬zhut be used as pressure gauges, vakuumetry, micromanometer.

Conclusions.

         Presented classification of instruments for measuring pressure and pressure measurement types for the principle of the obtained circuit connection and measurement parameters pressure and dilution of liquids and gases at rest and in motion.