MRK-D-0048 V4
Aeroqual Dust Sentry / AQS User Guide
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Zero calibration check and flow check of Particle Module
Tools required
R56, and DS R8 or AQM R7
Parts required
None
Service interval
Recommended
Monthly
. (See Section 6.1)
Online reference
training.aeroqual.com: Dust Monitor technical training Section 4.4
Online video
YouTube Channel: Aeroqual Service and Maintenance playlist
6.5.8.1
Check zero baseline of Particle Monitor
The Particle Monitor (nephelometer) has an automatic zero calibration function which runs every 12
hours, this procedure automatically changes the zero offset of the Particle Monitor.
The zero response of the Particle Monitor can be checked by removing the TSP head and placing the
R56 adaptor and zero filter assembly on the inlet above the cyclone as shown in Figure 6-18. The
Particle Monitor should read between ±3 µg m
-3
.
If the zero check shows negative numbers there may be a problem with the auto zero cycle. See the
troubleshooting section. Troubleshooting in Section.
Check that the gain and offset values for the Particle Monitor are set to sensible settings. The gain
should be between about 0.6 and 4.0. The offset should be 0.000.
See Section 7.2 for a discussion on gain adjustment of the Particle Monitor.
Figure 6-18 The zero filter is fitted above the cyclone for a Particle Monitor (left) and directly on the inlet
for a Particle Profiler (right)
6.5.8.2
Check the auto zero calibration flow rate of the Particle Monitor
The Particle Monitor executes an automatic zero calibration every 720 minutes (12 hours). The auto
zero process resets a parameter in the modules settings. The value which is changed is the H0
parameter.
NOTE:
The particle profiler does not have this feature.
The auto zero procedure on the Particle Monitor causes the baseline to be adjusted. Negative
readings on the Particle Monitor are often a result of the auto zero cycle failing to work correctly.
The zero cycle works by switching off the sample pump and switching on a zero pump. The flow rate
during the zero cycle is reversed and is a positive flow out through the inlet. The flow rate is
approximately 0.2 to 0.6 LPM.
This flow rate does not need to be set to a specific value but it is important that the flow rate is at least
0.2 LPM positive flow out from the inlet.