Pressure measurement elastic gauges

Pressure is measured extensively in the chemical processing industries and a wide variety of pressure measuring methods has been developed. Some of these have already been discussed in Volume 1, Section 6.2.2, viz. the manometer (which is an example of a gravity-balance type of meter), the Bourdon gauge (an example of an elastic transducer) and mention is made of the common first element in most pressure signal transmission systems—the differential pressure (DP) cell (Volume 1, Section 6.2.3). The latter also frequently forms part of a pneumatic transmission system and further discussion of this can be found in Section 6.3.4. 

In directly measuring vacuum gauges, the elastic restoring force of a spring element (diaphragm) or of gravitation (liquid column) is used for pressure measurement. 

In a diaphragm pressure gauge the elastic deflection of a circularly clamped metal disk is transferred to a pointer. Such devices are suitable for measuring ranges of 0-0.5 mbar and 0-70 bar [3]. For vacuum applications the range is 0-0.5 mbar and 0-1 bar vacuum. They are also suitable for differential pressure measurement if both sides of the diaphragm are connected with the respective measuring points. 

In many cases a Fortin-type barometer (Fig. M-13) is suitable. In this case the merexuy in the well is exposed to the atmosphere with the other end evacuated and sealed. All barometer readings shotdd be corrected for temperature, local gravity, and capiUary effect. Atmospheric pressure can also be measured by an aneroid barometer, which is a special type of elastic gauge. It is sometimes used in place of a manometer-type barometer because of the ease of transportation. 

Piezoresistive Sensors. The distinction between strain-gauge sensors and pie2oresistive (integrated-circuit) sensors is minor. Both function by measuring the strain on an elastic element as it is subjected to pressure. A pie2oresistive transducer is a variation of the strain gauge that uses bonded... 

Those that are based on the measurement of the distortion of an elastic pressure chamber (mechanical pressure gauges such as Bourdon-tube gauges and diaphragm gauges)... 

Further devices use strain-gauge transducers as so-called dead-end instruments or sensors mounted on a pipe with internal flow. The principle of this arrangement is the elastic deformation of a metallic cylinder, measured with the strain gauges. Pressures up to approx. 15 kbar can be measured [11]. 

The mechanical phenomena gauges measure the actual force exerted by the gas. They include a U-tube, a capsule dial, a strain, a capacitance manometer, a McLeod gauge, etc. Vacuum is measured according to the displacement of an elastic material or by measuring the force required to compensate its displacement. The measurement ranges from atmospheric pressure to 102 Pa in rough vacuum conditions. 

Barometry measures a broad variety of pressures using an equally broad variety of measurement techniques, including liquid column methods, elastic element methods, and electrical sensors. Electrical sensors include resistance strain gauges, capacitances, piezoresistive instruments, and piezoelectric devices. The technologies range from those developed by French mathematician Blaise Pascal, Greek mathematician Archimedes, and Torricelli to early twenty-first century MEMS sensors and those used to conduct nanoscale materials science. 

Besides the familiar Bourdon gauge, numerous instruments for the measurement of pressures have been described which are based on elastic deformation either of a diaphragm (of glass, of metal, or of a plastic ),... 

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