Installation manual

Publication 1747-RM001G-EN-P - November 2008
Proportional Integral Derivative Instruction 9-11
Example with the RG bit set: The reset term (TI) of 1 indicates that the integral
value of 0.01 minutes/repeat (0.6 seconds/repeat) is applied to the PID
integral algorithm. The gain value (KC) of 1 indicates that the error is
multiplied by 0.01 and applied to the PID algorithm.
Example with the RG bit clear: The reset term (TI) of 1 indicates that the integral
value of 0.1 minutes/repeat (6.0 seconds/repeat) is applied to the PID integral
algorithm. The gain value (KC) of 1 indicates that the error is multiplied by 0.1
and applied to the PID algorithm.
Setpoint Scaling (SC)
The SC bit is cleared when setpoint scaling values are specified.
Loop Update Time 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.
TIP
The rate multiplier (TD) is not affected by this selection.
Valid on SLC 5/03 and higher processors.
Table 9.14 Setpoint Scaling Parameter
Tuning Parameter
Descriptions
Address Data Format Range Type User Program
Access
SC - Setpoint Scaling Word 0, Bit
5
binary (bit) 0 or 1 control read/write
Table 9.15 Loop Update Time Too Fast Parameter
Tuning Parameter
Descriptions
Address Data Format Range Type User Program
Access
TF - Loop Update Too
Fast
Word 0, Bit 6 binary (bit) 0 or 1 status read/write