Dynamic SFC332L, Operator'S Manual

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Dynamic Flow Computers SFC332L Manual Data Entry
— 2-33
Date: 8/1/2019
PI D T
U N I N G
Flow Controller Gain
(Allowable Entries 0.0 – 9.99)
The gain is effectively 1/Proportional Band.
The basis of theory for proportional band is the relationship of the percentage of the output of the controller
to the percentage of the change of the process. In this case, if the control output changes 5% the flow rate
should change 5%, the proportional band would be 1.0 and the gain would be 1.0.
If the percentage of the output is 5% and the flow rate would change by 10%, the proportional band would
be 2 and the Gain would be 0.5
However since you do not know until you are flowing the effect of the output on the flow rate, you have to
start somewhere. A good starting point is to use a proportional band of 0.5 if the valve is properly sized.
Flow Controller Reset
(Allowable Range 0.0 – 9.99)
Reset is the number of minutes per repeat is the time interval controller adjusts the output to the final
control element. If the reset is set at 2, the flow computer will adjust the signal to the flow control valve
every 2 minutes. If the Reset is set at 0.3, the output signal will be adjusted approximately every 20
seconds, until the process and set point are the same.
The rule of thumb is the reset per minute should be set slightly slower that the amount of time it takes for
the control valve and the flow rate to react to the flow computer output signal changing.
This can only be determined when there is actual flow under normal conditions. It is best to start the reset at
0.3 or reset the signal every 3 minutes, if the control valve is properly sized.
Pressure Controller Gain
(Allowable Entries 0.0 – 9.99)
The gain is effectively 1/Proportional Band.
The basis of theory for proportional band is the relationship of the percentage of the output of the controller
to the percentage of the change of the process. In this case, if the control output changes 5% the pressure
should change 5%, the proportional band would be 1.0 and the gain would be 1.0.
If the percentage change of the output is 5% and the pressure would change by 10%, the proportional band
would be 2 and the Gain would be 0.5.
However since you do not know until you are flowing the effect of the output on the pressure, you have to
start somewhere. A good starting point is to use a proportional band of 0.5 if the control element is properly
sized.
Pressure Controller Reset
(Allowable Range 0.0 – 9.99)
Reset is the number of times per minute the controller adjusts the output to the control valve. If the reset is
set at 2, the flow computer will adjust the signal to the final control element every 2 minutes. If the Reset is
set at 0.3, the output signal will be adjusted approximately every 20 seconds, until the process and the set
point are the same.
The rule of thumb is the reset per minute should be set slightly slower that the amount of time it takes for
the control valve and the pressure to react to the flow computer changing the output.
This can only be determined when there is actually flow under normal conditions. It is best to start the reset
at 0.3 or reset the signal every 3 minutes, if the control element is properly sized.
Security Code
Several levels of security codes have been selected to fit different levels of responsibility. Up to six
alphanumeric codes can be used for each entry. If the security code is not used, then there will not be any
security code prompt in the menu.