The quantity “pressure” in a fluid (a liquid or a gas) is defined as “force divided by area”. The unit for pressure in the SI (Système International) is the “Pa” (Pascal), defined as 1Pa=1N/m2. Unfortunately, lPa is a very small pressure compared with the barometric pressure, which is about lOOkPa. Pressure encountered in most practical applications, especially in hydraulics and pneumatics, is always related to barometric (atmospheric) pressure. Because the unit “Pa” is not very convenient to use in these fields, the coherent unit “bar”, defined as 1bar= 1OOkPa (exactly) is widely used and also accepted by IS031-3:1992(E), item 3-15.1, for use in these fields. Therefore, in this book, the “bar” is used as the working unit for pressure.
KeywordsPressure Sensor Cylinder Pressure Piezoelectric Element Cavity Pressure Transduction Element
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