Technical Description 5-9
Note the particle concentration measured by the CPC is the total
number concentration of all particles that a CPC can detect. This
measurement provides no size differentiation and it is not corrected
using the CPC counting efficiency curve. When the CPC is used as
part of a Scanning Mobility Particle Sizer (SMPS, TSI Model 3936),
the counting efficiency curve is used to correct particle count data
to provide particle size distribution.
The 3775 CPC has a fast response time. T
95
, defined as the time it
takes for the CPC reading to reach 95% of a concentration step
change, is about 4 sec in high flow mode and about 5 sec in low
flow mode for the 3775 CPC.
Figure 5-3 shows the response time
curves in both flow modes. The curves are based on averaging of
three CPCs.
0
10
20
30
40
50
60
70
80
90
100
110
110100
Particle Diameter, nm
Counting Efficiency, %
Figure 5-2
Counting Efficiency Curve of 3775 CPC
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