3-2 | Model 120HD Hydrogen Analyzer
Electrical zero Adjustment
This adjustment must be made before the analyzer is used for the first
time but is necessary only occasionally after that.
For the
initial electrical zero adjustment
and all subsequent electrical zero adjust-
ments,
if the digital display does not read zero,
continue with the steps below.
1. Provide a low pressure (<5 PSIG), low flow rate source of air/nitrogen to
purge the gas passages in the analyzer of any residual gases from previous
tests.
2. Check and adjust the
CURRENT ADJUST
, if necessary.
3. Turn Knob 1 to the
TEST
position needed - either standard display or
backlit display (Figure 3-1).
4. Flow air or nitrogen through the analyzer.
5. The digital readout should settle at 0.0 within five minutes. If it does
not, adjust the Electrical Zero Adjust Screw #4 (Figure 3-1) until the
reading is 00.0. The 120HD is now ready to analyze a gas sample.
NOTE
Figure 3-1.
Front display with
adjustment knobs.
Displays % H2
(No Backlight)
Displays % H2
(Backlight)
Electrical Zero
Adjustment Screw
Displays
Sensor Current
(Backlight)
Current Adjustment
Knob
4
1
CURRENT ADJUST
SPAN ADJUST
(FOR CALIBRATION ONLY)
