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Bourdon tube pressure gauge consists of bourdon tube bent into an arc of circle. Cross-section of the tube is elliptical. One end of tube is connected to the point, whose pressure is to be measured. Other end is connected to the rack and pinion through mechanical linkage. The pointer is pivoted on the pinion (Fig. 1).
(a) Schematic view of Bourdon Tube Pressure Gauge.
The diaphragm is a thin plate of circular shape clamped firmly around its periphery. Also, it can be called as very thin membrane under radial tension.
Bellows is a longitudinally expansible and collapsible member consisting of several turns (convolutions) or folds. Thus, the bellows is a series of circular parts resembling the folds. Bellows has long length and it is made up of metal alloy, which ¡s ductile and retains its properties over long use. Commonly used materials are brass, bronze, beryllium, … Read more
lonization is the process of removing an electron from an atom producing a free electron and positively charged ion. Due to collision of high-speed electron from atom, ionization takes place in triode tube. An ionization gauge is used for measurement of very low pressure of the order of 1 micron and below. Construction of Ionization … Read more
Pirani gauge works on the principle that, “Thermal conductivity decreases with decreasing pressure.”
Pirani gauge is also a thermal conductivity gauge, like thermocouple vacuum gauge. Pirani gauge consists of a heating filament enclosed in chamber. Heating element or filament is a platinum wire, which forms an arm of Wheatstone bridge. Refer the Fig. 1.
Fig. 1: Pirani Gauge.
Thermocouple vacuum gauge operates on the principle of thermo-dynamics, which states that, “At low pressures, Thermal conductivity (Heat conductivity) decreases with decreasing pressure”.
Due to this property, thermocouple vacuum gauge can measure very low pressures, i.e. vacuum pressure (pressure below atmospheric pressure). Basically, thermocouple vacuum gauge measures the temperature of a heated element, called as heating filament surrounded by residual gas, connected to a vacuum system, whose pressure is to be determined.
McLeod gauge is a device used for the measurement of very low pressure. McLeod gauge comprises a system of glass tubing, in which, a known volume of gas at unknown pressure is trapped and then isothermally compressed by rising mercury column. This amplifies the unknown pressure and allows its measurement by conventional manometric means. It can measure the pressure of gas, which obeys the Boyle’s law i.e. P1V1 = P2V2.
Fig. 1: McLeod Gauge
