Bourdon tube pressure sensor

See next page for an overview diagram of the electrical system. There are two sensors in the system, the pressure switch with a bourdon tube sensor on the storage tank, and a fill level switch which controls the fluid level of the electrolyte. The fill level switch can be designed for a number of sensor options, including infrared and visible light photonic, with or without fiber optics capacitive inductive ultrasonic and others. 

The particular sensor/switch that we chose for this project has a bourdon tube to sense pressure and mechanically switch the signal current. It is an electromechanical switch. 

Pressure-sensing elements (a) flat diaphragm (b) corrugated diaphragm (c) capsule (d) bellows (e) straight tube (f) Cshaped Bourdon tube (g) twisted Bourdon tube (h) helical Bourdon tube (i) spiral Bourdon tube. (From Norton, H.N., Handbook of Transducers, Englewood Cliffe, NI Prentice-Hall, 1989, 294-330. Reprinted with permission.) Previously published in Chau, K.H.L., Pressure and sound measurement, in The Measurement, Instrumentation, and Sensors Handbook, Webster, I.G., Ed., CRC Press, Boca Raton, FL, 1999, p. 26-3.)... 

Classical pressure sensors are the purely mechanical pressure gauges (Table 14.2). Reasons for their wide use are robustness, low price, simple installation, and independence from electric power supplies. In the so-called Bourdon gauge, a dead-end tube in helical form with several turns expands due to elastic deformation when pressure is increased. This movement is transferred mechanically to a mostly circular scale. Although these instruments can be overloaded, it is common practice to operate them at no more than three-quarters of their full scale. These gauges are manufactured by a large number of companies and can be obtained in various qualities Table 14.3 gives advice on what to consider while choosing. 

Other types of these gauges include the twist tube, spiral tube, and helical tube. Diaphragm and bellows gauges are two other types of pressure sensor that were developed later. For more details on Bourdon tube materials and design, refer to Giacobbe and Bounds [1], Goitein [2], and Considine [3]. 

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