Publication 1766-RM001A-EN-P - October 2008
346 Process Control Instruction
Loop Update Too Fast (TF)
The TF bit is set by the PID algorithm if the loop update time specified
cannot be achieved by the controller due to scan time limitations.
If this bit is set, correct the problem by updating your PID loop at a
slower rate or move the PID instruction to an STI interrupt routine. Reset
and rate gains will be in error if the instruction operates with this bit set.
Derivative Action Bit (DA)
When set (1), the derivative (rate) action (DA) bit causes the derivative
(rate) calculation to be evaluated on the error instead of the process
variable (PV). When clear (0), this bit allows the derivative (rate)
calculation to be evaluated where the derivative is performed on the PV.
CV Upper Limit Alarm (UL)
The control variable upper limit alarm bit is set when the calculated CV
output exceeds the upper CV limit.
Tuning Parameter
Descriptions
Address Data Format Range Type User Program
Access
TF - Loop Update Too
Fast
PD10:0/TF binary (bit) 0 or 1 status read/write
Tuning Parameter
Descriptions
Address Data Format Range Type User Program
Access
DA - Derivative Action Bit PD10:0/DA binary (bit) 0 or 1 control read/write
Tuning Parameter
Descriptions
Address Data Format Range Type User Program
Access
UL - CV Upper Limit Alarm PD10:0/UL binary (bit) 0 or 1 status read/write
efesotomasyon.com - Allen Bradley,Rockwell,plc,servo,drive
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