Remote Set Point (Suffix Letter M) Operation; Auto/Manual Station (Suffix Letter E) Operation - Emerson Fisher KC Series Instruction Manual

4195KA, KB, KC, and KS Controllers
AUTOMATIC
POSITION
OUTPUT PRESSURE
TO FINAL CONTROL
ELEMENT
48A5230-A
A2999-1 / IL
the flapper where less input and more feedback
motion occurs, which decreases the gain of the
controller. Decreasing (narrowing) the proportional
band moves the nozzle toward a position where
more input and less feedback motion occurs, which
increases the gain. The controller action is changed
from direct to reverse by turning the proportional
band adjustment to position the nozzle on the
flapper quadrant to a point where the direction of the
flapper motion versus input motion is reversed as
shown in the flapper detail of figure 3-4. With the
controller in the reverse-acting mode, an increase in
process pressure causes a decrease in output
pressure.
Remote Set Point (suffix letter M)
Operation
The capability to adjust the controller set point from
a remote location is available with all 4195KA Series
controllers. This option is designated by the 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
adjustment via a connecting linkage. Increasing the
control pressure to the capsule increases the set
point setting and decreasing the control pressure
reduces the set point setting.
3-8
SUPPLY
PRESSURE
RELAY OUTPUT PRESSURE
SUPPLY PRESSURE
MANUAL LOADER OUTPUT PRESSURE
Figure 3-5. 4195KA Series Auto/Manual Station Schematic
AUTO/MANUAL
SWITCH
PLASTIC
TUBE
METAL BALL
RELAY
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 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
position, 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
it 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.
Instruction Manual
MANUAL LOADER
MANUAL
LOADER
KNOB
MANUAL
POSITION
AUTO/MANUAL
SWITCH
OUTPUT PRESSURE
TO FINAL CONTROL
ELEMENT
Form 5207
April 2007