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Aeroqual AQM60 User Guide
Recommended span concentrations for AQM sensor modules are as follows:
Gas
Span Point / ppm
O3
0.100
NO2, NOx
0.200
CO
5
VOC (isobutylene)
10
SO2, H2S
1
NMHC (isobutylene)
10
CO
2
1000
PID (isobutylene)
10
Certified calibration standards that can be used with the AQM include certified gas bottles, diluent
calibrators, or ozone calibrators.
4.4.1. Multi-Gas Calibration Standard and Gas Phase Titration
A three gas mixture that provides a convenient calibration standard for NO2, CO and SO2 is described in the
table below. Dilution by 100 with zero air and using a Gas Phase Titration (GPT) calibrator will provide the
required span points for NO2, CO, and SO2 simultaneously in a balance of air.
Note: NO2 should be generated using GPT with an excess of NO.
Gas
Concentration / ppm
NO
20
CO
500
SO2
100
Balance
Nitrogen
When performing NO2 calibrations using Gas Phase Titration it is better to use an excess of NO rather than
an excess of ozone. For a span point of 0.1 ppm NO2, the appropriate setting would be 0.2 NO and 0.1 O3
to produce 0.1 ppm NO2 and 0.1 ppm NO.
4.4.2. Span Calibration Procedure
1.
Connect the span calibration gas to the AQM through the sample port using ¼" Teflon tubing.
2.
Use a T fitting to ensure the AQM is sampling the gas flow at atmospheric pressure.
3.
The span gas flow should be > 3 LPM if using the R39.
4.
Check there is excess flow at the exhaust of the T fitting.
5.
Establish the correct concentration of gas using a reference analyser connected to the same
sample line.
6.
Set the span gas concentration to twice the required span for 30 minutes to saturate the sample
lines and then reduce by half to the required span.
7.
Allow the AQM to sample the gas until a stable reading is obtained (about 15 minutes).
8.
Calculate the new gain.
New Gain factor = Old Gain factor x Span Gas Concentration / AQM60 Gas Reading
9. Adjust the GAIN values for each gas se
nsor by clicking “Calibration”
“Calibrate GAIN”
Note 1
: The password to access this section is “password”
10. Select the relevant gas, input the new gain and click OK
Note 2:
The change is logged in the EVENTLOG file on the SD card.