5-2
Airnet® II 4-Channel Particle Sensors Operations Manual
Chapter 5
: Maintenance and Performance Checks
Background Count Check
•
Models 201-4, 301-4, 501-4: 0.085 to 0.115 CFM (± 5 %)
•
Models 310-4, 510-4: 0.085 to 1.15 CFM (± 5 %)
Background Count Check
Perform this check upon installation or when suspected contamination or noise-
induced counts may be causing inaccurate data. Background counts can be caused by
power line transients, cosmic ray particles, or RFI or EMI noise counts. Externally
induced counts are the exception; the only way to verify externally induced counts is to
perform this procedure.
To perform this procedure, you will need an absolute filter rated at less than 0.2 micron
(effective to 0.1 micron in air).
>> To perform a background count check:
1.
Locate the Airnet II 4-Channel particle sensor to where it will normally be used.
2.
Remove the isokinetic sample horn.
3.
Place the 0.2 micron absolute filter and inlet tubing adapter in series with the
sample inlet flow tube.
4.
Run six 10-minute samples.
5.
Verify that background count rates average less than ten counts per ten
minutes when using the specified filter.
6.
Return the instrument to normal operation by removing the filter from the
sample line.
