IM-P343-35 CTLS Issue 5
54
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TRANSLATION RUN OVER
SP500 Electropneumatic Smart Positioner
9.6.3 S-MAX - valve shut-off maximum
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Programming notes
Provides the facility to fully inflate the actuator at a pre-determined input signal. The value set is a percentage
of the input signal span range, i.e. setting a value of 10% with an input span range of 4 - 20 mA (16 mA),
will cause the valve to close with an input signal of 18.4 mA i.e. 20 mA - 1.6 mA (10% of 16 mA). Maximum
setting is 20%.
Default values will depend on the selection of valve type (2-port or 3-port) and control action (direct or
reverse) as follows:
Valve type Direct Reverse
2-port Off 0.1%
3-port 0.1% 0.1%
For direct action (dIRCT) can only be set if MAX-T = 100% (will inflate the actuator at set value). For reverse
action (REV) can only be set if MIN-T = 0% (will vent the actuator at set value).
Press and keys to alter displayed value. Press key to accept the displayed value and advance to the
characterisation (CHAR).
Commissioning notes
With an actual input signal of 20 mA and a maximum span range setting (MAX-R) of 20 mA may cause
the valve plug to hover over the seat preventing tight closure with the possibility of erosion damage to
the plug and seat. Setting a shut-off value can help prevent this by providing early closure of the valve.
9.6.4 CHAR - valve characterisation
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Programming notes
Provides selection of linear (LIN), equal percentage (EQUAL) or fast opening (FAST) characterisation.
Characterisation is the relationship between input signal and valve lift. Default value is Linear (LIN).
Use and keys to select the desired action. Press key to accept the displayed characterisation and
advance to time open (T-UP).
Commissioning notes
The standard characterisation for 2-port and 3-port valves is linear (LIN). For special applications using
2-port valves an equal percentage (EQUAL) or fast opening (FAST) characteristic can be selected.
With equal percentage the valve will start to open slowly and gradually accelerate opening related to
input signal. With fast opening characteristic the valve will commence to open quickly and gradually
slow down opening related to the input signal. This action is in addition to the valve trim flow
characterisation (refer to Figure 67 for guidance).
Fig. 67
Valve lift
Signal (mA)
Ratio 1:50
Ratio 50:1
Valve lift
Signal (mA)
Valve lift
Signal (mA)
Ratio 1:1
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