1-2 Model 3772/3771 Condensation Particle Counter
Figure 1-1 Figure 1-2
Model 3772 Condensation Particle Counter Model 3771 Condensation Particle Counter
(discontinued)
How it W o rks
In the Model 3772/3771 Condensation Particle Counter (CPC), an aerosol
sample is drawn continuously through a heated saturator in which butanol
is vaporized and diffuses into the sample stream. Together, the aerosol
sample and butanol vapor pass into a cooled condenser where the butanol
vapor becomes supersaturated and ready to condense. Particles present in
the sample stream serve as condensation nuclei. Once condensation
begins, particles that are larger than a threshold diameter quickly grow into
larger droplets and pass through an optical detector where they are
counted easily.
The Model 3772/3771 CPC detects particles as small as 10 nanometer in
diameter and employs single-particle-count-mode operation to measure
concentrations up to 10
4
particles per cubic centimeter. The detector
counts individual pulses produced as each particle (droplet) passes
through the sensing zone. A high signal-to-noise ratio and continuous, live-
time coincidence correction provide great measurement accuracy, even at
very low concentrations. An external vacuum pump is required to draw the
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