Instruction Manual

Instruction Manual
D200156X012
4194HA, HB, HC Controllers
September 2014
20
This method should only be used if pressure is not available to drive the differential pressure unit to 50 percent.
3. Remove the two machine screws (key 6) and lift off the proportional band indicator cover (key 36). Adjust the
proportional band adjustment between DIRECT and REVERSE.
4. The controller output should be 0.62 ±0.007 bar (9 ±0.1 psig) for a 0.2 to 1.0 bar (3 to 15 psig) output or 1.2 ±0.01
bar (18 ±0.2 psig) for a 0.4 to 2.0 bar (6 to 30 psig) output. If not, adjust flapper leveling screw number 2.
5. Adjust the proportional adjustment to 20 percent DIRECT (direct acting).
6. The controller output should be 0.62 ±0.02 bar (9 ±0.25 psig) or 1.2 ±0.04 bar (18 ±0.5 psig). If not, adjust flapper
leveling screw number 3.
7. Adjust the proportional band adjustment to 20 percent REVERSE (reverse acting).
8. The controller output should be 0.62 ±0.02 bar (9 ±0.25 psig) or 1.2 ±0.04 bar (18 ±0.5 psig). If not, adjust flapper
leveling screw number 1.
9. Repeat steps 5 through 8 until the output of the controller remains in tolerance without further leveling screw
adjustments.
10. If link 1 was disconnected, remove the tape and reconnect link 1 to the drive arm.
11. Set the proportional band adjustment to 400 percent in the desired controller action. Replace the proportional
band indicator cover (key 36) and install the machine screws (key 6).
Principle of Operation for 4194HA Controllers
Overall Operation
Refer to the schematic diagram in figure 3‐3.
Figure 3‐3. Schematic for Fisher 4194HA Controller
SET POINT
INDICATOR
PROCESS POINTER
REMOTE SET POINT
CONNECTED HERE
INPUT ELEMENT
CONNECTED HERE
CONNECTING
LINK
BEAM
FLAPPER
NOZZLE
PROPORTIONAL
BELLOWS
RESET BELLOWS (VENTED)
PROPORTIONAL
BAND ADJUSTMENT
SUPPLY
PRESSURE
RELAY
OUTPUT PRESSURE
TO FINAL CONTROL
ELEMENT
REVERSE ACTION
QUADRANT
FLAPPER
PIVOT
FEEDBACK
LINK
FEEDBACK
MOTION
DIRECT ACTION
QUADRANT
INPUT MOTION
FLAPPER DETAIL
SUPPLY PRESSURE
OUTPUT PRESSURE
NOZZLE PRESSURE
46A9764‐C
B1907