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7.2.2
Reference Array Parameters
Note: Machine Edition software allows you to modify the configurable parameters for a PID
instruction in real time in online programmer mode. To customize PID parameters, right click
the PID function and select Tuning.
Words
1
Loop Number
(Address+0)
Optional number of the PID block. It provides a common identification
in the CPU with the loop number defined by an operator interface
device.
2
Algorithm
(Address+1)
1 = ISA algorithm
2 = Independent algorithm
3
Sample Period
(Address+2)
The shortest time, in 10ms. Increments, between solutions of the PID
algorithm. For example, use a 10 for a 100ms. Sample period.
Minimum time of 10ms is enforced by the block if the sweep<10ms)
4,5
Dead Band +
Dead Band –
(Address+3,
Address+4)
Integral values defining the upper (+) and lower (-) Dead Band limits. If
no Dead Band is required, these values must be 0. If the PID Error (SP -
PV) or (PV - SP) is above the (-) value and below the (+) value, the PID
calculations are solved with an Error of 0. If non-zero, the (+) value
must greater than 0 and the (-) value less than 0 or the PID block will
not function.
Leave these at 0 until the PID loop gains are set up or tuned. A Dead
Band might be added to avoid small CV output changes due to
variations in error.
6
PID_IND: Proportional Gain (Kp)
PID_ISA: Controller gain (Kc = Kp)
(Address+5)
PID_IND: Change in the control variable in CV Counts for a 100 PV
Count change in the Error term. Entered as an integer representing a
fixed-point decimal ratio with two decimal places. Displayed as a ratio
of percentages with two decimal places.
For example, a Kp entered as 450 is displayed as 4.50 and results in a
Kp * Error / 100 or 450 * Error / 100 contribution to the PID Output.
PID_ISA: Same as PID_IND.
Kp is generally the first gain set when adjusting a PID loop.
GFK-2950C
Parameter/Description
February 2018
Chapter 7. PID Built-In Function Block
Low Bit
Units
Integer
-
10ms.
PV
Counts
%CV/%PV
Range
0 to 255 (for
user display
only)
Set by the CPU
0 (every
sweep) to
65535
(10.9 Min) At
least 10ms.
Dead Band +: 0
to 32767
(never
negative)
Dead Band -: -
32768 to 0
(never
positive)
0 to 327.67%
33
C
V
%
/
P
V
%
347
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