Rockwell Automation 1771-PD PID MODULE (+DU) - Manual (Page 71)

Programming
Chapter 3
3Ć28
W25(W45) Derivative Gain, K D (Rate Term, Td). If W02 B00 is
reset, the module uses the A-B value K D and this word contains the
derivative gain constant for the loop. If W02 B00 is set, the modules uses
the ISA value Td and this word contains the rate term for the loop. Data
format is 4-digit BCD, 99.99 in units of seconds (A-B) or minutes (ISA),
with implied decimal point. Multiplier bits W19(W39)B03, B02 can be
selected by 1, divided by 10, x10, x100 (Table 3.F). By using multipliers,
the range can be extended from 0.000 to 9999.
W26(W46) Integral Term Limit, V I MAX. This word contains the
integral term limit for the loop. It can be used for alarm purposes and/or
limiting. The alarm condition is indicated by W61(W68)B10. Integral
term limiting is selected by B10 = 1 in word W18(W38). Data format is
4-digit BCD with a range from 0000 to 9999.
NOTE: When limiting is selected, lowering the value of V I MAX
reduces the PID module’s ability to adjust the integral term. The
performance of bumpless transfer could be hindered.
W27(W47) Derivative Term Limit, VD MAX. This word contains the
derivative term limit for the loop. It can be used for alarm purposes
and/or limiting. The alarm condition is indicated by W61(W68)B02.
Derivative term limiting is selected by B02 = 1 in word W18(W38). Data
format is 4-digit BCD with a range from 0000 to 9999.
W28(W48) Minimum Output Limit, VMIN. This word contains the
minimum limit for the analog output that is determined by the PID
module’s algorithm. This value can be used for alarm purposes and/or
limiting. The alarm condition is indicated by W61(W68)B01. Output
limiting is selected by B16 = 1 in word W19(W39). Data format is 4-digit
BCD with range from 0000 to 4095. This limit has no effect on a SET
OUT value downloaded from the PC processor into word W05(W12).
W29(W49) Maximum Output Limit, VMAX. This word contains the
maximum limit for the analog output that is determined by the PID
module’s algorithm. This value can be used for alarm purposes and/or
limiting. The alarm is indicated by W61(W68)B00. Output limiting is
selected by B16 = 1 in word W19(W39). Data format is 4-digit BCD with
a range from 0000 to 4095. This limit has no effect on a SET OUT value
downloaded from the PC processor into word W05(W12).
NOTE: The following words, W30(W50) through W36(W56), can be
programmed if the expanded features (XF) of the loop are selected by