23
Reference Information
Manifold Sample Flow
The manifold operates as shown in figure 11
.
Figure 15. Manifold Theory of Operations
The external vacuum pump provides between 40-80 in/
H
2
O vacuum at the large fitting on the rear
of the manifold
. This vacuum produces a 2-3 cfm flow rate at each of the 32 manifold ports
.
The particle counter only draws 1 cfm through the sample line and selected port via the sample
pickup shoe
, allowing the excess sample to flow around the pickup shoe. This positive pressure
and flow around the pickup shoe is what prevents ambient air from being sampled by the counter.
Any ambient air that enters the manifold system
will be drawn into the external vacuum pump
rather than the Particle Counter because of the dominant flow pattern in the internal cavity.
(x32)
1 Cfm to particle
counter
=
Excess sample flow
Sample
pickup
shoe
