The Bourdon pressure gauge operates on the principle that, when pressurized, a flattened tube tends to straighten or regain its circular form in cross-section. The Bourdon tube comes in C, helical, and spiral shapes—although most gauges employ the C shape.
Pressure Sensor Diaphragm Designs
The diaphragm can be used as a means of isolating the process fluids, or for high- pressure applications. It is also useful in providing pressure measurement with electrical transducers..
A Strain gauge (sometimes refered to as a Strain gage) is a sensor whose resistance varies with applied force; It converts force, pressure, tension, weight, etc., into a change in electrical resistance which can then be measured. When external forces are applied to a stationary object, stress and strain are the result.
Potentiometric Pressure transducer, there is a potentiometer which is made by winding resistance wire around an insulated cylinder. A movable electrical contact, called a wiper, slides along the cylinder, touching the wire at one point on each turn. The position of the wiper determines how much wire, and therefore, how much resistance, is between the end of the wire and the wiper. A mechanical linkage from the pressure-sensing element controls the position of the wiper on the potentiometer.
Diaphragm Pressure GaugesDiaphragm Pressure Gauges are used to measure gases and liquids. They cover measuring spans from 10 mbar to 40 bar. The measuring element consists of one circular diaphragm clamped between a pair of flanges.
A diaphragm seal is a flexible membrane that seals and isolates an enclosure. The flexible nature of this seal allows pressure effects to cross the barrier but not the material being contained. Common uses for diaphragm seals are to protect pressure sensors from the fluid whose pressure is being measured.
Bourdon Tube PressureBourdon tube pressure gauges are the most common type in many areas and are used to measure medium to high pressures. They cover measuring spans from 600 mbar to 4,000 bar. The measuring element is a curved tube with a circular, spiral or coiled shape, commonly called a bourdon tube.
The gauge is attached to the object by a suitable adhesive, such as cyanoacrylate. As the object is deformed, the foil is deformed, causing its electrical resistance to change. This resistance change, usually measured using a Wheatstone bridge, is related to the strain by the quantity known as the gauge factor.