TSI Instruments SidePak AM520, User Manual

Page: 64 / 98

Chapter 4 48
Using and Maintaining the Diesel Particulate Matter
DPM Cyclone
The DPM Cyclone included with the AM520/AM520i can be used to
differentiate between the diesel particulate matter and other portions
of the ambient aerosol. It is ideal for making breathing zone
measurements because it can be attached to clothing near the
wearers face/breathing zone. TSI
®
supplies a U-tube, clip, and a Dorr-
Oliver cyclone with the DPM cyclone specifically for this purpose.
The DPM cyclone is designed with a 50 percent cut-off size of
0.8 µm. The Dorr-Oliver cyclone is positioned upstream of the DPM
cyclone to filter out particles larger than 4 µm preventing large
particles from clogging the inlet of the DPM cyclone.
The cyclone works by forcing the particle-laden air sample to swirl
inside the cyclone body. Larger (higher mass) particles cannot follow
the air stream and become trapped while smaller particles stay in the
air stream and pass through. When using the cyclone, you can
assume that all particles smaller than the cut-off size pass through
and all larger particles become trapped in the grit potentiometer.
The cut-off size for any cyclone is dependent on flow rate.
N O T I C E
It is very important that the sample flow rate through the SidePak
™
monitor be set at 1.7 liters per minute (L/min). If some other flow
rate is set, the cut-off size will be unknown.