A gauge with a thin metal or ceramic diaphragm that deflects under the pressure difference between the process side and a sealed high vacuum reference, changing its capacitance to a fixed electrode. Because it measures force per area directly, the reading does not depend on gas composition, which is why process tools use it for pressure control. Each head covers about four decades below its full scale, such as 1000, 10 or 0.1 Torr, and precision heads are heated for stability and need periodic zeroing.
Zero the 100-millitorr cap manometer at base before the run, it's drifted three percent since last week.
Fab techs call any capacitance manometer a Baratron after the best-known brand, and they zero it only at a pressure far below its resolution, never at process pressure.
Also heard as
- CDG
- capacitance diaphragm gauge
- cap manometer
- Baratron
Related terms
Pirani gauge
Thermal conductivity gauge that reads pressure from how quickly gas carries heat away from a hot wire.
Gas correction factor
Multiplier that converts a gauge reading calibrated for nitrogen into the true pressure of another gas.
Ionization gauge
Gauge that reads high and ultra-high vacuum by ionizing gas molecules and measuring the resulting ion current.