- Problems on conventional B-A gauges with pollutants.
- Contaminated grid
- Increase of emission power
- shorten the life time of filaments
- Contaminated collector
- Degrade its sensitivity
- wrong measurement of pressure
- usually measure lower than real pressure.
- Typical sources of contaminants
- Plasticiser evaporation
- -> Pthalic acid, Adipic acid
- Wires, motors and seals
- -> Siloxiane
- Metal Organic gases in Semiconductor Production machine
- -> Residual photoresist
Structure of the B-A Tough Gauge©
Thermoelectron which came out of a filament goes into the Grid. (Emission Current: Ie). Thermoelectron hits a gas molecule. Then, positive ion arises and gathers for the collector. (Ion current:Ii)
* Ii = S x Ie x P (S is a sensitivity coefficient and invariable.)
Pressure can be known, if Ie is kept constant and Ii is measured.
Tough Gauge© vs Conventional B-A Gauge
Performance of the sensitivity in Siloxane.