Diaphragm pressure gauges are considered as specialists along the way industries. They enter into play when Bourdon tube pressure gauges reach the limits of their performance. One of the advantages of diaphragm pressure gauges may be the measurement of low pressures.
Diaphragm pressure gauges could be recognised from the first look: From the flanges below the case, between that your elastic pressure element ? the diaphragm element ? is clamped. These instruments can measure pressures from only 16 mbar, with the utmost value at around 25 bar (for comparison: Bourdon tube gauges reach their lowest physically possible measured value at 600 mbar). The larger the diaphragm element, the lower the measurable pressure is, in accordance with the formula ? pressure = force / area. WIKA uses two diaphragm sizes: with a diameter of 134.5 mm for the measuring ranges of 0 ?16 mbar around 0 ? 250 mbar and a diameter of 76.5 mm for the measuring ranges of 0 ? Quality around 0?25 bar.
Special variation of diaphragm pressure gauges
With pressures under 16 mbar, diaphragm pressure gauges hit their limits. Because of this case, their diaphragms would need to be exceptionally thin to experience the required elasticity. Then, however, they might no more remain reliably stable. This problem could be solved, though, with a special variation of the diaphragm pressure gauge: the capsule pressure gauge.
Capsule elements consist of two diaphragms welded together, which are generally loaded with pressure from the within. This results in a double diaphragm travel. In this manner, even the lowest of pressures can be measured without reducing the wall thickness. However, since the pressure chamber isn’t self-draining, capsule elements aren’t suitable for applications with liquid media.
Note
In The Zone can find more info on diaphragm pressure gauges on the WIKA website under the headings Pressure gauges and Pressure gauges with output signal.
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Advantages of diaphragm pressure gauges (2): High overload protection