Installation manual

Publication 1747-RM001G-EN-P - November 2008
Proportional Integral Derivative Instruction 9-7
Rate Term (T
d
)
Rate T
d
(word 5) is the Derivative term. The adjustment range is 0 to 327.67
minutes. Set this value to 1/8 of the integral gain T
i
.
Feed Forward/Bias
Applications involving transport lags may require that a bias be added to the
CV output in anticipation of a disturbance. This bias can be accomplished
using the processor by writing a value to the Feed Forward/Bias element, the
seventh element (word 6) in the control block file (See page 9-5.) The value
you write is added to the output, allowing a feed forward action to take place.
You may add a bias by writing a value between -16383 and +16383 to word 6
with your programming terminal or ladder program.
Mode (TM)
The mode bit specifies when the PID is in timed mode (1) or STI mode (0).
This bit can be set or cleared by instructions in your ladder program.
When set for timed mode, the PID executes and updates the CV at the rate
specified in the loop update parameter (word 13).
Table 9.5 Rate Term Parameter
Tuning Parameter
Descriptions
Address Data Format Range Type User Program
Access
TD - Rate Term - T
d
Word 5 word (INT) 0 to 32,767 control read/write
TIP
This word is not affected by the reset and gain range (RG)
bit. For information, see Reset and Gain Enhancement Bit
(RG) on page 9-10.
Table 9.6 Mode Bit Parameter
Tuning Parameter
Descriptions
Address Data
Format
Range Type User Program
Access
TM - Mode Word 0, Bit 0 binary 0 or 1 control read/write