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Vacuum System
5
Foreline gauge
Foreline gauge
The foreline gauge monitors the pressure (vacuum) at the exit of the diffusion
pump. The primary function of the foreline gauge is diffusion pump control.
When the foreline pump has reduced the pressure in the vacuum manifold to
below
300 mTorr (0.3 Torr), the diffusion pump is automatically switched on. If the fore-
line pressure rises above 400 mTorr (0.4 Torr), the ac board switches off the diffu-
sion pump heater and the analyzer electronics.
The foreline pressure can be monitored from your data system.
The turbo pump MSD does not require a foreline gauge. Instead, the motor speed
is monitored.
See Also
To view MSD temperature and vacuum status, page 36
Gauge controller, page 208
Table 2. Typical MSD pressure readings for various carrier gas flow rates,
page 45
196
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