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Aeroqual AQM60 User Guide
4.2. AQM Calibration Basics
Zero and span adjustments on the AQM60 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 AQM can be calibrated in the unit by applying certified gas to the AQM
inlet.
All zero and span calibrations or checks should be performed with gas mixtures in a balance of air.
Note 1: The calibration standard may be in a balance of N2 but it should be diluted by at least 50x
with air before exposing to the AQM.
Fluorocarbon (PTFE, FEP or PFA) tubing and fittings should be used for all sample lines.
The AQM is supplied with a thermal management system to maintain a stable internal temperature.
Calibrate the AQM with the door closed to enable the unit to stabilize at its correct temperature.
Note 2:
Warm up the AQM for at least 12 hours before attempting a gas sensor calibration
4.2.1 Nafion Humidifier (AQM R21)
Aeroqual’s GSS sensor calibration can be adversely affected by the very dry (dew point < -30
o
C) air typically
generated by calibration sources. Hence Aeroqual has developed the AQM R21 Calibration Humidifier to
humidify calibration gases without affecting the calibration gas concentration. It contains a nafion membrane
from Permapure (
) which allows the transport of water molecules across the membrane
with high selectivity. This humidifier should be used for all zero and span gas calibrations.
Instructions
1. Remove the lid and fill the humidifier with clean water up to the top of the label, covering the black
internal tubing. Refit the lid.
2. Connect the gas outlet line from your dilution calibrator to one of the inlets of the AQM R21 and
connect the other inlet of the AQM R21 to a T fitting as per the diagram in section 4.3.
3. Set the calibration gas flow to a flow rate of between 3-5 LPM to generate a humidity level of 25 to
40% RH at an indoor temperature of 22
o
C.
Do NOT use a humidifier
:
If the relative humidity of the zero air generator and diluted span gas is greater than 10% or if the
dew point of the ambient air at the measurement site is typically less than -5
o
C.
Do use a humidifier:
If the relative humidity of the zero air generator and diluted span gas is less than 10 % and the dew
point of the ambient air at the measurement site is typically greater than -5
o
C
Important Notes
1. Always operate the R21 at dew points below the internal operating temperature of your
AQM60 (typically ITemp = 28
o
C) to avoid condensation.
2. If the ambient temperature is high you may need to reduce the amount of water inside the
humidifier so that a shorter length of the membrane is submerged in order to achieve an
appropriate RH.
Summary of Contents for AQM60
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