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7 Operating the mini-OPC
The mini-OPC measures the optical size and number concentration of particles in the
0.15 to 3 micron diameter size range by detecting the light scattered from individual par-
ticles. The mini-OPC is an extremely sensitive measurement device, capable of high size
resolution number size distribution measurements at 2Hz under a broad range of con-
centration conditions.
Practicing good electrostatic discharge (ESD) procedures and understanding proper dry-
ing of the particle sample flow are two key aspects of properly operating the mini-OPC.
The exposed circuit boards of the unit are susceptible to ESD damage, be sure to install
the provided grounding strap and to ground yourself prior to handling the device.
Particle size depends on the relative humidity (RH) of the air around the particles since
most particles take up water via condensation and grow when exposed to elevated RH. If
water is evaporating from particles during sizing in the mini-OPC then the particle size
is not stable and a 'true' size will not be determined. Be sure to dry the particle sample
flow to RH's below 20% before entering the device.
There are three ways to interact with the mini-OPC; the mini front panel, through the
UAV Reader GUI program which runs on a windows computer or via the RS232 port.
The mini-OPC provides raw size-bin number counts, raw number concentrations versus
size, and number size distributions (dN/dlogDp) in real time when using the UAV Reader
software to interact with the unit. Monitor the flow rates, temperature and pressure
during operation to confirm proper operating conditions.
7.1 Electrostatic Discharge Practices
The mini-OPC employs an extremely sensitive detector capable of measuring extremely
small electrical signals. To protect the detector, good ESD practices are critical to main-
taining and operating your device.
• Be sure to always ground yourself before handling the unit
• Be sure to always connect the unit to earth ground
83-00032-01
7
Operating the mini-OPC
mini-OPC 9405
Page 19 of 39
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