4-6 Model 3022A Condensation Particle Counter
Question Answer Explanation
Ref 2.000–
5.000v
This is the reference photodetector.
Potentiometer RA1 has been set to maximum
so the display reads 2 to 5 volts. Press the
Display button.
Flow Cal? N
Y
No
Yes: Answering yes requires an external means
of measuring the flow to calibrate the internal
volumetric flowmeter; see “Flow Calibration”
below.
5.00 cm
3
/s
128
Follow instructions under “Condenser Flow
Calibration” below.
Zero flow The pump switches off. Wait 30 seconds until
the flow is absolutely zero. Press Display. After
a brief delay, the front panel momentarily
displays “Set Up Done.” Exit the configuration
mode.
Flow Calibration
Since the flow calibration is more complicated than described
above, a few extra words of guidance are in order.
The calibrated flow is measured by the pressure drop across a
capillary tube. The pressure drop at 5.00 cm
3
/s is approximately
0.48 inch of water. It is measured with a sensitive transducer that
has a voltage output of 0 to 5V; this corresponds to 0 to 1 inch of
water. When you calibrate the flowrate of the CPC, you are
programming the microprocessor to maintain a specific pressure-
transducer voltage. The pump voltage is adjusted to maintain a
steady pressure drop, which in turn maintains a constant
volumetric flow through the CPC.
The calibration is done at two points only: zero flow and 5.00
cm
3
/s. Other flowrates that may be displayed on the front panel are
calculated on the basis of physical principles and normalized to the
calibrated points. These other flows may not be accurate but are
used simply to show that the flow is either too high or too low and
by an approximate amount.
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