10-2 Model 3022A Condensation Particle Counter
Testing Filter Efficiency
The CPC is ideal for testing the efficiency of filters because of its
high concentration limit of 9.99× 10
6
particles/cm
3
and its extreme
accuracy at low concentrations. At high concentrations there is no
need for a diluter. Since the CPC detects nearly 100 percent of
particles above 0.02 micrometer, the CPC can detect all particles in
the size range of interest.
The filter testing paper in Appendix C describes the use of a CPC
for testing filters. The CPC discussed here is very similar to the
Model 3022A CPC.
Using the CPC With a Diffusion Battery
The CPC measures the number concentration of an aerosol, but
gives no information about its size distribution; the droplet size is
independent of the size of the initial particle. A diffusion battery
separates particles according to their size for particle diameters
below about 0.2 micrometer. For a more complete measurement of
the concentration and size distribution of an aerosol, operate the
CPC in series with a diffusion battery.
TSI’s Model 3040/3042 Diffusion Battery and Switching Valve
consists of a diffusion battery with a pump, flowmeter, and
automatic switcher for sampling successive ports in the battery.
The system in Figure 10-1 automatically steps through the ports to
make repeated measurements of the concentration and size
distribution of any test aerosol smaller than 0.2 micrometer. Use
the CPC’s low-flow mode and plug the makeup air when sampling
from the diffusion battery or switching valve.
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