G. Calibration and Zero Checks
Model AQSync Air Quality Monitoring Station Manual Rev. A-1
40
2. After the instrument is warmed up, make note of the time and collect data for 5
to 10 minutes.
3. Access the data for that time interval using the web interface and compute the
average.
4. The observed ozone offset, which can amount to
a few ppb, can be corrected
for by changing the offset calibration parameter from the Settings/Ozone
Settings/Cal Settings touchscreen. The offset is applied in units of ppb (integer
numbers only).
Note the number currently displayed as the “Zero.” Click on it to
bring up the keyboard that will enable you to change it as needed. For example:
If during your zero check the instrument reads an average of +3 ppb with the
external scrubber in place, the instrument is reading too high by 3 ppb.
Therefore, the value of the offset should be decreased by 3 from its present
value.
5. Remove the ozone scrubber from the inlet tubing and restore the original
plumbing connection to the sampling bulkhead on the AQSync.
G.2.2
CO
2
Instrument
The
CO
2
instrument
is
the
PPSystems SBA-5 CO
2
Gas
Analyzer (link to user manual in
Appendix 1). The.CO
2
instrument
has a built-in zeroing system and
periodically carries out a zero,
including at startup. From the
main screen, click on “CO
2
Status
”
to view whether the zero is
occurring.
The frequency of the zeroing is set
to 6 hours (360 mins) and the
duration is 40 seconds. The zeroing occurs by passing the air sample through a soda-
lime filter. With a zeroing frequency of 6 hours at a duration of 40 seconds, the soda
lime will need replacement approximately every 6 months of continuous operation at
typical ambient levels of CO
2
. Please see Section H of this manual for maintenance
procedures.
If the measurements of ambient CO
2
seem to be consistently going below 400 ppm, it
suggests that the soda lime in the scrubber should be replaced, or the CO
2
module’s
zero valve is not working properly.
G.2.3
Particle Instrument
The particle instrument is a Met One Model 83214 AQ Mass Profiler (link to user manual
in Appendix 1). This instrument is zeroed and calibrated by Met One. It is
