Principle Of Operation For 4195Kb And Kc Controllers; Overall Operation - Emerson Fisher 4195KA Instruction Manual

4195K Controllers
July 2018
differential pressure or counterclockwise to increase the differential pressure. The differential relief valve is set at
the factory to relieve at approximately 0.4 bar (5 psi) differential pressure.
13. Repeat steps 7 through 12 until the required differential pressure is obtained.
Calibration for the differential relief valve to relieve on falling controller output pressure
1. Provide a means of measuring the controller output pressure by connecting the controller output to a pressure
gauge (open‐loop conditions must exist). Do not apply supply pressure at this time.
2. Set the reset adjustment to 0.01 minutes per repeat (wide open) and the rate adjustment (4195KC controllers only)
to the OFF position.
3. For a controller with manual set point, move the set point indicator to the mid‐scale mark on the process scale. For
a controller with remote set point, adjust the remote set point pressure until the set point indicator is at the
mid‐scale mark on the process scale.
4. Set the proportional band to 100 percent in either the DIRECT or REVERSE action depending on the application
requirements.
5. Refer to figure 4‐3 for the location of the anti‐reset windup differential relief valve. For the differential relief valve to
relieve on falling controller output pressure, install the valve so the arrow on the valve points up. To change the
direction of the arrow, loosen the two mounting screws, pull the valve out, and reinstall the valve with the arrow
pointing up. Tighten the two mounting screws.
6. Provide a regulated supply pressure to the controller. Do not exceed the normal operating pressure in table 1‐6.
Note
Because of the high controller gain with the reset adjustment at 0.01 minutes per repeat, the controller output will not balance
perfectly in the following step. If the controller output is stable for approximately 5 seconds, it is adequately balanced.
7. Increase the process pressure (or vacuum for a vacuum controller) to the controller until the controller output
pressure balances at 0.8 bar (12 psig) for a 0.2 to 1.0 bar (3 to 15 psig) output range or 1.6 bar (24 psig) for a 0.4 to
2.0 bar (6 to 30 psig) output range.
8. Turn the reset adjustment to the CLOSED (4195KB controllers) or OFF (4195KC controllers) position.
9. Decrease the controller output pressure in small steps [approximately 0.04 bar ( 0.5 psig)] by changing the process
pressure to the controller or by changing the controller set point. After each change in controller process pressure
or set point, the controller output pressure should quickly change and then stabilize at the new value.
10. Continue to change the controller output pressure in 0.04 bar (0.5 psi) steps and check the output pressure after
each step to make sure it stabilizes. At some point, the controller output will start to ramp downward to 0 bar (0
psig) with no further change to the controller input or set point. Record the controller output pressure where this
ramping action begins because this is the point at which the differential relief valve has relieved.
11. To obtain the differential relief valve differential setting, calculate the difference between the original controller
output pressure in step 7 and the controller output pressure recorded in step 10.
12. If the differential pressure calculated in step 11 is incorrect for the application, adjust the differential pressure by
turning the differential relief valve adjustment screw, shown in figure 4‐3. Turn the screw clockwise to decrease the
differential pressure or counterclockwise to increase the differential pressure. The differential relief valve is set at
the factory to relieve at approximately 0.4 bar (5 psi) differential pressure.
13. Repeat steps 7 through 12 until the required differential pressure is obtained.

Principle of Operation for 4195KB and KC Controllers

Overall Operation

Refer to the schematic diagram in figure 4‐5 for 4195KB controllers, or to the schematic diagram in figure 4‐6 for
4195KC controllers.
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Instruction Manual
D200160X012