Configuring the CPC 4-7
When calibrating the flow, chose an external flowmeter that will
have a low pressure drop and measure the actual volumetric flow. If
you use a mass flowmeter (one calibrated to standard conditions),
convert the standard flow to actual flow with the following equation:
Actual flow (cm / s) = std flow (cm / s)
293
33
××
T
P
10135.
where: T = ° Kelvin
P = kPa.
Condenser Flow Calibration
To calibrate the condenser flow follow these four steps:
1. When the display on the counter reads “Cond Cal? N,” press
the Total button until the “N” changes to “Y.” Press the Display
button to continue the calibration. If you answered yes to the
calibration, the display changes to “5.00 cm
3
/s 128.” This
indicates the target flow into the counter inlet (5.00 cm
3
/s) and
the power to the pump (0–255), initially set at 128.
2. Connect a flowmeter to the inlet of the CPC and measure the
flow. If the flow is higher than 5.00 cm
3
/s, press the Total
button repeatedly (the 128 number will decrease) until the
external flowmeter reads 5.00 cm
3
/s. If the flow is lower than
5.00 cm
3
/s, press the Range button repeatedly (the 128
number will increase) until the external flowmeter reads 5.00
cm
3
/s.
Note: The condenser flowmeter voltage is available at the Analog
Output for reference.
3. When the flow is correct (as measured by the external
flowmeter), press the Display button to record the operating
voltage of the internal flowmeter.
4. The display now reads “Zero Flow.” Allow the pump to come to a
complete stop (30 seconds) and then press the Display button
to record the zero-flow voltage of the internal flowmeter. The
display now asks whether the aerosol flow should be calibrated.
Answering yes requires that the aerosol flow be calibrated as
outlined below. Answering no allows you to exit the calibration
procedure and return at a later time.
Note: Both flows should be calibrated before using the counter.
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