Ametek PMT 40, Руководство пользователя

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User Manual
5
PROPOR RESET + RATE
CONTROLLER (Fig. 10)
The function of the three mode controller
(proportional, reset and rate) is to eliminate off
set, increase stability and reduce stabilization
time. With the rate and reset valve in series (reset
restriction following rate restriction) over-shooting
on start-up and instability due to too much
resetting action are prevented because rate time
will never exceed reset time.
With the reset valve closed the instrument acts
as a two mode controller (propor rate) as
described in the previous section. As the reset
valve is partially opened, output air is metered
into the air chamber outside of the capsule
causing the feedback to respond to the error
between the process and set point.
In Fig. 10, with the nozzle and proportional dial in
the positions shown, the propor reset +
rate controller will be reverse acting.
Determine whether a rise in pressure should open
or close the valve. Position the nozzle as shown
in table and rotate the proportional dial so that
the green pointer is in the “A” or “B” sector for a
given controller.
REVERSING ACTION
Supply air to controller is necessary for this
operation. Loosen nozzle screw one half turn and
rotate nozzle until it is pointing squarely at flapper
blade. Tighten screw. Turn proportional dial to
appropriate zone.
If output gauge does not show full supply
pressure when flapper is held against nozzle,
readjust nozzle.
NOTE: When changing the Control Action, make
sure the alignment of the nozzle and flapper are
parallel to each other. This helps ensure proper
operation. Pinching the flapper against the
nozzle should make output pressure go to max
pressure (supply pressure).
SELECTION OF CONTROL ACTION
IF AN INCREASE
IN PRESSURE
MUST
AND THE
ACTION OF THE
VALVE IS
THEN THE
ACTION OF THE
CONTROLLER
MUST BE
AND THE
NOZZLE
POSITION
MUST BE
AND FOR THE FOLLOWING CONTROLLERS THE
GREEN POINTER IS IN ZONE
PROPORTIONAL
PROP. + RESET OR PROP.
+ RESET + RATE OR
DIFFERENTIAL GAP
CLOSE VALVE AIR TO CLOSE
DIRECT A-WHITE B-BLACK
OPEN VALVE AIR TO OPEN
CLOSE VALVE AIR TO OPEN
REVERSE B-BLACK A-WHITE
OPEN VALVE AIR TO CLOSE