Principle Of Operation - Emerson Fisher 3610J Instruction Manual

Instruction Manual
D200149X012
Figure 18. Flow Characteristics for the Various Cams When Used With an Equal Percentage Valve Characteristic
Push‐Down‐to‐Close Valve
PUSH DOWN TO CLOSE
DIRECT
REVERSE
33A4960‐A PERCENT OF RATED INPUT SPAN
A1582‐3

Principle of Operation

3610J positioners accept a pneumatic input signal and 3620J positioners accept a DC current input signal from a
control device. 3620J electro‐pneumatic positioners use a 3622 converter to provide a pneumatic input to the
pneumatic portion (3610J) of the positioner. 3610J positioners are force‐balanced instruments that provide a control
valve position proportional to the pneumatic input signal. The following describes the principle of operation for 3610JP
and 3620JP positioners. The principle of operation for 3610J and 3620J positioners is similar except relay A is not used.
The principle of operation for 3611JP and 3621JP positioners is similar except the feedback linkage does not use a cam.
Refer to the schematic diagrams as indicated:
D 3610J—figure 19
D 3610JP—figure 20
D 3611JP—figure 21
D 3620J—figure 22
D 3620JP—figure 23
D 3621JP—figure 24
For direct action, input signal pressure from a control device is channeled to cavity A in the input module. An increase
in input signal pressure results in a downward force on the summing beam, pivoting the summing beam
counterclockwise. This moves the flapper slightly toward the nozzle, increasing the nozzle pressure. As nozzle pressure
increases, the relay beam pivots clockwise, causing relay B to increase actuator upper cylinder pressure and relay A to
exhaust actuator lower cylinder pressure to atmosphere.
CAM
C
CAM
A
CAM
B
3610J and 3620J Positioners
September 2017
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