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SET POINT INDICATOR
PROCESS POINTER
REMOTE SET POINT
CONNECTED HERE
INPUT ELEMENT
CONNECTED HERE
CONNECTING
LINK
BEAM
SUPPLY PRESSURE
OUTPUT PRESSURE
PROPORTIONAL PRESSURE
NOZZLE PRESSURE
46A9764-A
B1489-2 / IL
Remote Set Point (suffix letter M)
Operation
The capability to adjust the controller set point from a
remote location is available with all 4194A Series con-
trollers. This option is designated by the suffix letter M
in the type number.
A control pressure is applied to the capsular element
within the remote set point assembly. The expansion
and contraction of the capsule moves the set point
indicator via a connecting linkage. Increasing the con-
trol pressure to the capsule increases the set point
setting and decreasing the control pressure reduces
the set point setting.
Auto/Manual Station (suffix letter E)
Operation
A controller with the auto/manual station (designated
by the suffix letter E in the type number) has piping on
the output side of the relay as shown in figure 3-5.
Supply pressure to the relay is also applied to the
manual loader. The manual loader, functioning as a
RESET BELLOWS (VENTED)
PROPORTIONAL
BELLOWS
FLAPPER
NOZZLE
Figure 3-4. 4194A Series Controller Schematic
4194A, B, and C Series
PROPORTIONAL
BAND ADJUSTMENT
FEEDBACK
LINK
FEEDBACK
MOTION
DIRECT ACTION
QUADRANT
SUPPLY
PRESSURE
regulator, applies pressure to one side of the plastic
tube and to the auto/manual switch. Output pressure
from the relay registers on the other side of the plastic
tube as well as in the auto/manual switch.
When the auto/manual switch is in the MANUAL posi-
tion, the manual loader output is channeled through
the auto/manual switch and becomes the controller
output. When the auto/manual switch is in the AUTO
position, the relay output is channeled through the
switch to become the controller output.
Before the auto/manual switch is operated, the relay
output must equal the manual loader output to avoid
bumping the process. Adjusting the set point varies
the pressure on the left-hand side of the plastic tube.
Adjusting the manual loader knob varies the pressure
on the right-hand side. When the pressures are equal,
the metal ball is centered in the tube and is held in
place by a small magnet. A pressure imbalance forces
the ball to one end of the tube where it forms a seal,
blocking air flow through the tube.
REVERSE ACTION
QUADRANT
FLAPPER PIVOT
INPUT
MOTION
OUTPUT PRESSURE
TO FINAL CONTROL
ELEMENT
RELAY
3–7
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