Electrical Zero Adjustment - Ametek 120HD User Manual

Figure 3-1.
Front display with
adjustment knobs.
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.
NOTE
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.
Displays
Sensor Current
(Backlight)
Electrical Zero
Adjustment Screw
CURRENT ADJUST
Current Adjustment
Knob
(FOR CALIBRATION ONLY)
Displays % H2
(No Backlight)
Displays % H2
1
(Backlight)
4
SPAN ADJUST