Why is the impactor flow rate set at 30 lpm and the screen on the laptop says something different?
The impactor takes 30 lpm volumetric flow to achieve a 1-um cutpoint. What is being displayed in cpdclient is a calibrated, mass flow rate. So even if the true volumetric flow through the system was 30.0, the displayed flow would not equal 30.0, unless the temperature at the sensor is 0 degrees C, the pressure is 1013.25 mb, and the calibration ratio (true flow/measured flow) is exactly 1:1 with no offset. If you are reading the value displayed by the #4 PID in the Filter Rack#2 PID box, then what you are reading is an UNCALIBRATED, mass flow measurement of the flow through the filter. If you are reading the flow displayed on the aerosol laptop (“Q Filter (slpm)” in the “Filter-2” window in cpdclient), then you are reading a CALIBRATED mass flow measurement of the flow through the filter.
