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The Pirani gauge consists of a metal sensor wire (usually gold plated tungsten or platinum) suspended in a tube which is connected to the system whose vacuum is to be measured. The wire is usually coiled to make the gauge more compact. The connection is usually made either by a ground glass joint or a flanged metal connector, sealed with an o ...
The widely used Bourdon gauge is a mechanical device, which both measures and indicates and is probably the best known type of gauge. A vacuum gauge is used to measure pressures lower than the ambient atmospheric pressure, which is set as the zero point, in negative values (for instance, −1 bar or −760 mmHg equals total vacuum). Most gauges ...
A glass McLeod gauge, drained of mercury. A McLeod gauge is a scientific instrument used to measure very low pressures, down to 10 −6 Torr (0.133 mPa). It was invented in 1874 by Herbert McLeod (1841–1923). [1] McLeod gauges were once commonly found attached to equipment that operates under vacuum, such as a lyophilizer. Today, however ...
Air pressure in an automobile tire relative to atmosphere (gauge pressure) [citation needed] +210 to +900 kPa +30 to +130 psi Air pressure in a bicycle tire relative to atmosphere (gauge pressure) [57] 300 kPa 50 psi Water pressure of a garden hose [58] 300 to 700 kPa 50–100 psi Typical water pressure of a municipal water supply in the US [59]
Further, the vacuum in the gauge eventually deteriorates due to slow diffusion of gases through the mercury, making the device inaccurate. [8] In 1938, Adolph Zimmerli (1886–1967) [9] invented a gauge that overcame the filling problems, at least for pressures below ambient pressure. [10] Zimmerli's gauge consists of three relatively wide columns.
At the heated sides the particles that interact will gain kinetic energy and push to plate to rotation. By reading the speed of this rotation the pressure can be determined. (This is an interpretation from the information about Knudsen manometer from the Dutch book Vacuum Technologie [1])
The reading is taken from the scale marked next to the grooves, in dimensionless "Hegman units" (or National Standard units; NS) and/or mils or micrometres. [5] Hegman units are defined in terms of an inverted size scale as shown below: [6] Hegman Grind Gage and doctor blade Paint sample at top of Hegman Hegman after paint drawdown