Agilent Technologies IMG-500 Manual page 23

Compact Cold Cathode Gauge IMG-500
Ignition Delay
When cold cathode measurement systems are activated upon
switching the gauge on, an ignition delay occurs, which is typi-
cally:
-7
10 mbar
-8
10 mbar
-9
2×10 mbar
Contamination
Gauge failures due to contamination or wear and tear, as well as
expendable parts (e.g. seals), are not covered by the warranty.
Gauge contamination is influenced by the process media used
as well as any existing or new contaminants and their respective
partial pressures. Continuous operation in the range of
-4 -2
10 mbar ... 10
as reduced up-time and maintenance cycles. With constantly low
pressures (< 1×10
than one year without cleaning (cleaning the gauge   [1]).
In general, contamination of the gauge leads to deviations of the
measured values:
 In the low pressure range (p < 1×10
dication is usually too low (as a consequence of the contami-
nation of the cold cathode system). In case of severe contami-
nation, instabilities can occur (layers of the measuring cham-
ber peel off). Contamination due to isolating layers can even
lead to a complete failure of the discharge.
Contamination can to a certain extent be reduced by:
 geometric protection (e.g. screenings, elbows) against parti-
cles that spread rectilinearly
 mounting the flange of the gauge at a place where the partial
pressure of the pollutants is particularly low.
Special precautions are required for vapors deposited under
plasma (of the cold cathode measuring system). It may even be
necessary to temporarily switch of the gauge while vapors occur.
0.1 minute
1 minute
5 minutes
mbar can cause severe contamination as well
-6
mbar), the gauge can be operated for more
23
-3
mbar), the pressure in-