Editing Pressure measurement (section)

====Diaphragm (membrane) {{anchor|Diaphragm|Membrane}}====
A second type of aneroid gauge uses [[Deflection (engineering)|deflection]] of a flexible [[Artificial membrane|membrane]] that separates regions of different pressure. The amount of deflection is repeatable for known pressures so the pressure can be determined by using calibration. The deformation of a thin diaphragm is dependent on the difference in pressure between its two faces.  The reference face can be open to atmosphere to measure gauge pressure, open to a second port to measure differential pressure, or can be sealed against a vacuum or other fixed reference pressure to measure absolute pressure. The deformation can be measured using mechanical, optical or capacitive techniques. Ceramic and metallic diaphragms are used.
The useful range is above 10<sup>−2</sup> [[Torr]] (roughly 1 [[Pascal (unit)|Pa]]).<ref name=schoonoverinc>[https://web.archive.org/web/20040102031317/http://schoonoverinc.com/PDFs/Sky%20Brochure.pdf Product brochure from Schoonover, Inc]</ref>
For absolute measurements, welded pressure capsules with diaphragms on either side are often used.
Membrane shapes include:
* Flat
* Corrugated
* Flattened tube
* Capsule