How an MKS Baratron® Capacitance Manometer Works
The Sensor Capsule
The sensor capsule contains the diaphragm and the metal-on-ceramic electrode structure. The reference side (backside) of the diaphragm is evacuated to a very
high vacuum, much lower than the pressures that are to be measured. The high
vacuum on the reference side is maintained over the life of the manometer by means
of an internal chemical getter pump. The sensors are made of Inconel® all-welded construction for ruggedness and compatibility with process environments.
Pressure is determined by measuring the change in capacitance between the metal
diaphragm and an adjacent, fixed dual electrode. The radially tensioned diaphragm
provides very low hysteresis, excellent repeatability, remarkably high resolution
(1x10-5 of Full Scale), fast response, and the ability to measure extremely low
pressures.
If a high overpressure is applied to the manometer, the diaphragm will bottom out
on the electrode substrate, preventing permanent damage to the sensor. Most MKS
Baratron® capacitance manometers have an overpressure rating of 45 psia or 2-times
the Full Scale range, whichever is greater. Pressures of greater than the allowable
rating can cause internal mechanical failure or significant changes in the zero.
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