Envent Engineering Ltd. Page 28 Revision 2.4
CALIBRATION PROCEDURES
H
2
S Gas Calibration
Depending on the application, the 330S/331S H
2
S analyzer will require more or fewer
periodic calibrations. There is no specific time as to how often the H
2
S analyzer
should be calibrated. It will depend on the application, importance of accuracy for the
application, and how dirty or clean the environment and sample are. The following is
the calibration procedure for the 330S/331S H
2
S analyzer:
1. Source a calibration gas of H
2
S in balance of N2 regulated to 15 psi (check expiry
date). H
2
S concentration to be approximately 2/3 of full scale range or close to
the H
2
S alarm set point.
2. Press the bypass button and verify the "Bypass" LED illuminates (alarms will be
held in the non- alarm state).
3. Turn off all gas supplies to the analyzer and check that a sufficient amount of H
2
S
sensing tape is installed.
4. Press the "Menu/Set" button until "Mtr Run" is displayed. Press the right arrow
[→], the H
2
S sensing tape will advance for approximately 10 seconds.
Press the "Menu/Set" button until "mV" is displayed ("###mV"). If the mV reading is
1000mV (+100mV), proceed to the next step, otherwise re-zero sensor (Refer to "
5. Re-zero Sensor Procedure" on page 29).
6. Connect calibration gas to calibration port and turn the 3-way calibration valve
180°. The valve handle should be pointing towards where the gas bottle tubing is
connected to (Calibration Inlet).
7. Turn on sample inlet valve, ensure that the sample regulator is supplying 15psig
to the eductor (make sure there is suction from the eductor block). Adjust the flow
meter to 2.0. Wait until the H
2
S reading has stabilized (10 to 15 minutes).
8. With calibration gas applied, if H
2
S reading is satisfactory (+2% of analyzer full
range) skip to step 16, if H
2
S reading is not satisfactory a gain adjustment is
required, continue to step 9.
9. Press the "Menu/Set" button until the gain setting is displayed ("### Gain").
10. Calculate the new gain. New gain value should be within approximately 25% of
the gain installed at the factory.
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