4
Pneumatics:
Refer to the figure 2 for pneumatics block diagram. Tubing from the areas to be
monitored and from a reference air source (either fresh, outside air, or interior conditioned air
that is free of refrigerants) is connected to the valve manifold. The MCD1 has a single sample
valve and a reference valve, for a total of two valves. The MCD4 has four sample valves, the
MCD8 has eight and the MCD16 has 16, for a total of five, nine and seventeen valves
respectively. The electronics alternates between energizing the Sample air and the Auto zero
air valves. Following an Auto zero cycle, the pneumatics will be switched to the next sample
valve in order. The diaphragm pump draws air from the selected inlet and feeds the air
through a five micron filter, through an orifice restrictor, through the infrared bench and to the
exhaust port located on the lower right side of the unit. The pressure switch monitors the
pressure created by the flow from the pump and the restriction created by the orifice. Should
pressure fall, a flow failure is detected, and signal is sent to the electronics.
IR
B
e
n
c
h
Press. Switch
D
ia
p
h
ra
g
m
P
u
m
p
Valves
Area 1
Reference Air
Area 5
Area 6
Area 2
Area 4
Area 7
Area 8
Area 3
Exhaust
Figure 2 Pneumatics Diagram
Summary of Contents for IR-SNIF-MC-1
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