Type 846 and Model 3311
Instruction Manual
Form 5739
February 2002
4–2
Figure 4-1. Functional Parts Block Diagram
4 to 20 MA
INPUT
ELECTRONIC CIRCUIT
MAGNETIC ACTUATOR
PILOT STAGE
BOOSTER STAGE
SOLID-STATE
PRESSURE
SENSOR
TO VALVE ACTUATOR
3 TO 15 PSI
OUTPUT, TYPICAL
A6324-1/IL
Figure 4-2. Detail of Deflector/Nozzle Pilot Stage
W6287/IL
Figure 4-3. Deflector/Nozzle Pilot Stage Operation (Direct Action)
HIGH OUTPUT PRESSURE
PRESSURE TO
BOOSTER STAGE
REGULATED
AIR SUPPLY
LOW OUTPUT PRESSURE
DEFLECTED NOZZLE
FLOW PATTERN
PRESSURE TO
BOOSTER STAGE
REGULATED
AIR SUPPLY
A6645/IL
Booster Stage
The receiver nozzle pressure controls the booster
stage, which has a poppet valve design. An increase
in receiver nozzle pressure positions the valving in
the booster stage to produce an increase in the
transducer output signal. A decrease in the receiver
nozzle pressure positions the valving in the booster
stage to allow exhaust to occur, decreasing the
output signal.
The booster stage operates using a 3:1 pressure
gain from the pilot stage. High flow rate capability is
achieved by large flow area poppet design and
internal porting having low flow resistance. The
booster stage design provides very good stability in
high vibration applications, and the poppet valve
technology provides resistance to plugging.