Emerson Fisher 3610J Instruction Manual page 32

3610J and 3620J Positioners
September 2017
Figure 19. Schematic of Fisher 3610J Positioner
MINOR LOOP
GAIN ADJ
FLAPPER
NOZZLE
FIXED
RESTRICTION
38A8901‐B
B1844‐1
As a result, the actuator rod extends and the actuator rotary shaft rotates clockwise. This causes the feedback lever to
pivot clockwise increasing the force applied to the summing beam by the range spring. This force, which opposes the
downward force on the summing beam caused by the increasing input signal pressure, continues to increase until the
summing beam torques are in equilibrium. At this point, the valve shaft is in the correct position for the specific input
signal applied.
For reverse action, input signal pressure is channeled to both cavities A and B. An increase in input signal pressure
results in an upward force on the summing beam, pivoting the summing beam clockwise and causing relay B to
exhaust actuator upper cylinder pressure to atmosphere and relay A to increase actuator lower cylinder pressure. As a
result, the actuator rod retracts and the actuator rotary shaft rotates counterclockwise. This causes the feedback arm
to pivot counterclockwise reducing the force applied to the summing beam by the range spring.
As the valve shaft rotates counterclockwise, the range spring force on the summing beam continues to reduce until
the summing beam torques are in equilibrium. At this point, the valve shaft is in the correct position for the specific
input signal applied.
The 3620J positioner is a combination of a 3610J positioner with a 3622 electro‐pneumatic converter. The
electro‐pneumatic converter provides a 0.2 to 1.0 bar (3 to 15 psig) output pressure proportional to the 4 to 20
milliampere DC input signal. The 0.2 to 1.0 bar (3 to 15 psig) output pressure becomes the input signal pressure to the
3610J pneumatic positioner.
32
CROSS‐OVER ADJ
RELAY
A
ZERO ADJ
COARSE
SPAN
ADJ
SUMMING BEAM
CAVITY A
CAVITY B
INPUT SIGNAL
PRESSURE
AIR SUPPLY
POSITIONER CAM
END VIEW OF
ROTARY SHAFT
RELAY BEAM
RELAY
B
AIR
SUPPLY
RANGE SPRING
COUNTER SPRING
PIVOT A
INPUT MODULE
PIVOT B
FEEDBACK
LEVER
SPRING AND DIAPHRAGM
ACTUATOR
Instruction Manual
D200149X012
SUPPLY PRESSURE
NOZZLE PRESSURE
INPUT SIGNAL
OUTPUT SIGNAL
FINE
SPAN
ADJ