IQM 60 V5 Pump Revision October 2010
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5.1.2 Zero verification using Gas Treatment Module
The Gas Treatment Module contains a zero air scrubber which can be automatically or manually turned on
to periodically measure the zero of the instrument. The automatic zero verification is set in the
Configuration file under Zero Readings. This turns on the gas treatment module for 30 minutes during
which time the sensors continue to measure. This procedure is repeated at a user defined interval between
1 and 255 hours. It is recommended that this procedure is used when making field measurements.
5.1.3 Zero calibration
5.1.3.1 Using Gas Treatment Module
You may use the zero air scrubber in the Gas Treatment Module to undertake a manual zero calibration.
Before doing this you should check that the media are in good condition or if possible replace with fresh
media.
1. Turn on the zero scrubber manually by clicking on PC software, Tools- >Turn On Zero Scrubber.
2. Allow the AQM to sample until stable readings are obtained (about 30 - 60 minutes).
3. Adjust the OFFSET values for each gas sensor via the Calibration --> Calibrate OFFSET-->enter
password “password”--> select gas--->enter new OFFSET
new OFFSET = old OFFSET + AQM60 gas reading
5.1.3.2 Laboratory Zero calibration
The IQM can be re-zeroed via the PC software using a zero air source with relative humidity of 50% +/-
20%. Aeroqual can supply a humidifier that uses a Nafion membrane to humidify the air.
1. Connect a source of zero air to the IQM through the sample port using ¼ inch Teflon tubing. Use a
T fitting to ensure the IQM is sampling the gas flow at atmospheric pressure. The zero air should
be at least 1.5 LPM (check there is excess flow at the exhaust of the T fitting).
2. Allow the IQM to sample until stable readings are obtained (about 30-60 minutes).
3. Adjust the OFFSET values for each gas sensor via the Calibration --> Calibrate OFFSET-->enter
password “password”--> select gas--->enter new OFFSET
new OFFSET = old OFFSET + AQM60 gas reading
5.1.4 Span calibration
The sensors can be manually span calibrated by modifying the individual gain factors for each sensor.
Introduce a known concentration of span gas into the instrument and adjust the gain factor to set the
correct concentration reading. Note: a sensor zero point calibration should always be performed before
undertaking a span calibration.
5.1.4.1 Span gas
Span gas mixtures should be
single
gas mixtures that are certified and be in a
balance of air
.
DO NOT USE MIXTURES THAT CONTAIN MORE THAN ONE SPAN GAS COMPONENT
DO NOT USE A SPAN GAS IN A BALANCE OF NITROGEN UNLESS DILUTION IS GREATER
THAN 50 TIMES WITH ZERO AIR.
The mixture should also be humidified to about 50 +/-20% RH by either using a Nafion membrane
humidifier or by bubbling the zero grade air through water prior to mixing with the gas standard. Aeroqual
can supply a Nafion humidifier which is suitable for IQM units containing O3, NO2, CO, SO2 and VOC
sensor modules. Excessive gas concentrations should be avoided as these may damage the sensors or
cause contamination of the internal tubing. Recommended span points for gas sensors are given in the
table below.
