FRG-700 Inverted Magnetron Pirani Gauge
23
Problem Possible
cause
Remedy
Measuring signal
continually < 0.5 V
"Error low".
No supply voltage.
Turn on the power
supply.
Measuring signal
continually > 9.5 V
"Error high".
Pirani measurement
element defective
(filament rupture).
Replace the Pirani
element (
→
21).
Electronics unit not cor-
rectly mounted.
Mount the electronics
unit correctly (
→
21).
The green lamp is ON and
the identification indicates
Pirani-only mode (mea-
suring signal continually
> 4.0 V)
"Pirani underrange".
The cold cathode dis-
charge has not ignited.
Wait until the gas dis-
charge ignites (in case of
contamination with insu-
lation layers, the cold
cathode may completely
fail to ignite).
(Cleaning
→
19).
The FRG has only been
activated with
p < 3×10
—9
mbar.
Slightly increase the
pressure.
Measuring signal con-
tinually > 5 V or display
> 10
-3
mbar although
vacuum pressure is OK.
Pirani measurement cir-
cuit not adjusted, e.g.
due to severe contami-
nation.
Readjust the Pirani
measurement circuit
(
→
17). If adjustment
is impossible, replace the
Pirani element.
Measurement
of
heavy
gases.
Convert with the corre-
sponding formula
(
→
27).
Severe outgassing in the
cold cathode measuring
chamber.
Clean the measuring
chamber.
Measuring signal unstable. Gauge contaminated.
Clean the gauge
(
→
19).
6.3 Troubleshooting
