5-8 Model 3022A Condensation Particle Counter
Figure 5-2
Flow Schematic of the CPC
High Flow
The high-flow option allows the sample to be brought to the CPC
faster; this minimizes response time and diffusional particle losses.
In the high-flow mode, the three-way valve is opened to the bypass
flow, the flow of makeup air is shut off. A total of 1.5 liters per
minute (±10%) is drawn into the CPC’s inlet. The flow splits so that
0.3 liter per minute flows through the sensor and 1.2 liters per
minute flows through the bypass. Together, the flowmeter and
microprocessor control the vacuum pump to maintain the flowrate
through the condenser (Flow on front panel). The accuracy of the
sensor flow is based on a two-point calibration at 0 and at 0.3 liter
per minute.
Low Flow
The low-flow option allows the minimum flowrate when a high flow
is undesirable, for example, when using the CPC with the
Differential Mobility Particle Sizer (DMPS) system or the Scanning
Mobility Particle Sizer (SMPS) system. In the low-flow mode, the
three-way valve is open to the flow of makeup air, the bypass flow is
shut off. Only 0.3 liter per minute is drawn into the inlet and
carried directly into the sensor.
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