Pressure piston manometer

The piston manometer is a primary standard gauge that balances the pressure on one arm in a piston-cylinder arrangement by the addition of... 

Usually, the force, F, is generated by the dead weight on a piston with well-defined area. A, as illustrated in Fig. 2.2. Accurate determinations of the effective area, and corrections for friction and for the buoyancy of the piston require great care if the best possible (absolute) accuracies are required (that is, accuracies of the order of 10 p.p.m (parts per million) ). For practical applications, other secondary pressure gauges (manometers) are used they are usually commercially calibrated, or they can be recalibrated, if necessary, by comparison with transfer standards. ... 

General Case.—Consider a mass m of a gas enclosed in a cylinder fitted with a piston and in connexion with a manometer capable of indicating very rapid changes of pressure (Fig. 21). Let p0 be the initial pressure. 

For coloured vapours (bromine) an optical method, depending on measuring the refractive index by an interferometer, has been used. Scott used the Langmuir vibrating quartz-fibre manometer ( 14.VII A) for alkali metals. Fouretier, for Small pressures, used a curved tube containing a dishshaped piston with a small clearance, operating a lever moving a mirror. 

Fig. 1.6 A cross section of a 1.6 GPa cylinder (B) to experimental cell, (C) compression chamber (diameter, 16 mm), (H) piston head, (1) inner cylinder under radial compression, (M) to resistance manometer, (P) high-pressure outlet plug with electrical leads, (U) unsupported-area, Bridgman-type, sliding-piston arrangement. The force applied to the piston by the oil ram for a pressure of 1.6 GPa is F= 350 kN.

An original route is that proposed by Ter-Minassian and Million in 1983 [44] with their pneumatic compensation calorimeter, represented in Fig 10. The tubular sample cell 4 is in good thermal contact with four metallic bulbs. Two of them operate like bulb 1 in the figure, Le. as pneumatic thermal detectors. They are filled with gas, say around 1 bar, and their pressure is compared, by means of a differential manometer, with the constant pressure of a reference reservoir 3 immersed in the surrounding thermostat block 5. Therefore, they detect any temperature change of the sample. The two oflier bulbs operate like bulb 2, i.e. as pneumatic energy-compensating devices. They are also filled with gas, say around 1 bar, but they are connected to flie piston-cylinder 7 which enables the heat of compression (or decompression) necessary to cancel the temperature difference between the sample and thermostat (as detected with the first set of bulbs) to be produced in the bulb. More recently, Zimmermaim and Keller built a comparable pneumatic compensation calorimeter whose calorimetric performances were carefully examined [45]. 

A working pressure sensor linked via chained calibrations to a standard liquid manometer or piston gauge maintained by an NMI... 

Figure 6 Apparatus for determination of vapour pressure by dynamic method, A, Monel boiler provided with central thermometer pocket B, aluminium tube-oven C, coupling linking metal connecting tube to glass D, mercury-filled manometer connected to oil-filled line leading to piston gauge E, glass valve with PTFE stem Fisher and Porter Company, U.S.A.) F, reservoir for introduction of the sample G,H, electrical heater windings K,L, control resistor windings, insulated by suitable wrappings from G and H M, platinum resistance thermometer N, connection to vacuum system...

The work produced by a system concerns gas compression and/or expansion. For this purpose, we can imagine cylinder with diameter S with a piston under which there is a gas (Figure 3.13). There is a manometer to measure pressurep. The cylinder has a ruler on its side to measure piston position (i.e., volume). We shall act on the piston by a force F. Under the action of this force the piston, having compressed gas, will move on dx. The work of the force under gas we shall define as t/A = Fdx. Since pressure is p = F/S then F = pS and dA = pSdl is the change of volume under the piston dl S = dV. The work of external force dA is equal to the increase of the system s potential energy... 

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