FRG-700 Inverted Magnetron Pirani Gauge
23
4.3 Adjusting
the
Gauge
The gauge is factory-calibrated. If used under different climatic
conditions, through extreme temperatures, aging or contamina-
tion, and after exchanging the sensor, the characteristic curve
can be offset and readjustment may become necessary.
The cold cathode measurement circuit, which is dominant for low
pressures (<1×10
-3
mbar), is factory-calibrated. By way of con-
trast, the Pirani measurement circuit can be adjusted. Any ad-
justment has a negligible effect on the pressure range between
approx. 10
-2
mbar and 10
2
mbar.
n
If you are using a seal with centering ring and filter, check
that they are clean or replace them if necessary (
→
"Dein-
stallation").
o
Activate the gauge.
p
Evacuate it to p << 10
-4
mbar and wait at least 10 minutes.
q
Turn the nameplate counter-clockwise until the mechanical
stop is reached.
