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SERIES 3000 MKII TECHNICAL MANUAL
8.2.2 Zeroing and span calibration of Hydrogen Sulfide sensors
Hydrogen Sulfide sensors can be affected by extreme humidity changes. A sudden increase in ambient
humidity can result in a short-term positive drift in the instrument's reading. A sudden decrease in ambient
humidity can result in a short-term negative drift in the instrument's reading. These are most likely to
be noticed during calibration with dry or cylinder gas.
When calibrating Hydrogen Sulfide cartridges the following should be taken into account while following
the procedure in 8.2.1:
1. To zero the sensor, use a compressed air cylinder of 20.9%Vol oxygen (not Nitrogen). Do not use
background air.
2. Apply the gas to the sensor for three minutes before using '' to confirm the zero calibration.
3. If a span calibration is to be performed, the span calibration gas should be applied to the sensor
immediately after the zeroing procedure. Do not allow the sensor to return to ambient air conditions
between steps 2 and 3.
4. Apply the span gas for two minutes before using '' to confirm the span calibration.
8.2.3 Zeroing and span calibration of Ethylene Oxide sensors
Ethylene Oxide sensors can be affected by extreme humidity changes. A sudden increase in ambient
humidity will result in a short-term positive drift in the instrument's reading. A sudden decrease in
ambient humidity will result in a short-term negative drift in the instrument's reading. These are most
likely to be noticed during calibration with dry or cylinder gas.
When calibrating Ethylene Oxide sensors the following should be taken into account while following
the procedure in 8.2.1:
If the sensor is to be zero calibrated only (no span calibration), the calibration should be performed in
clean ambient air or cylinder air (not Nitrogen) humidified to approximately ambient humidity levels.
If performing a full calibration (zero and span) the following procedure should be used:
1. Apply clean, dry air (not Nitrogen) to the sensor for 5 minutes. Do not use background air.
2. Zero the sensor using '✓' to confirm the zero calibration.
3. Apply the span calibration gas to the sensor immediately after the zeroing procedure. Do not
allow the sensor to return to ambient air conditions between steps 2 and 3.
4. Apply the span gas to the sensor for five minutes before using '✓' to confirm the span calibration.
5. After the span calibration, the sensor should be allowed to recover in clean ambient air, or cylinder
air humidified to approximately ambient humidity levels for fifteen minutes and then should be zero
calibrated under these conditions. Note that this does not affect the span sensitivity of the instrument.
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