IQM 60 V5 Pump Revision October 2010
11
5.0 Calibration
5.1 Gas
Module
Calibration
All the Gas modules in the IQM can be calibrated in the unit by applying certified gas to the IQM inlet. All
Zero and span calibrations or checks should be performed with humidified air and use single gas mixtures
in a balance of air. If the IQM is to be deployed in environments with very low or high absolute humidity it is
recommended that the sensors be zero and span calibrated under those conditions, since the sensors are
slightly sensitive to changes in absolute humidity.
Zero and span adjustments on the IQM60 V5 are performed by adjusting the OFFSET and GAIN values
under the Calibration menu. The equation that relates the OFFSET and GAIN to the Gas reading is given
below:
Gas Reading = GAIN x (Module Reading - OFFSET)
All the Gas modules in the IQM can be calibrated in the unit by applying certified gas to the IQM inlet.
All zero and span calibrations or checks should be performed with gas mixtures in a balance of
air. Note: the calibration standard may be in a balance of N2 but it should be diluted with air
prior to presenting to the IQM.
Fluorocarbon (PTFE, FEP or PFA) tubing and fittings should be used for all sample lines
.
Warm up the IQM for at least
12 hours
before attempting a gas sensor calibration
5.1.1 Nafion Humidifier
A Nafion tubing membrane humidifier is supplied with the IQM which can be used to humidify the air
delivered to the IQM during calibrations. Two lengths of 1/4” Teflon tubes are supplied to enable
connection to sample lines and the IQM inlet.
Span gas and zero air is typically dry (~0%RH) and the sensors used in the IQM require 50 +/-20% RH for
best performance. The Nafion membrane is selectively permeable to water vapor (although some other
compounds such as ammonia, alcohols, acetone, and acetic acid may also be transported across the
membrane see
www.permapure.com
for further information) and the direction of transport is driven by the
concentration gradient across the tubing wall. The humidifier is designed to extract water vapor from the
surrounding ambient air and transfer this into the dry span or zero gas source. The resultant humidity in the
sample gas is roughly half of that of the ambient air. If the surrounding air humidity is less than 50% it is
recommended that the membrane is positioned above a water bath to increase the humidity in the sample
air. Also, Make sure that the air surrounding the membrane is not contaminated with hydrocarbons that
could be transported across the nafion to the sensors. If in doubt contact Aeroqual.
Nafion humidifier
