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User Manual
GFK-1503F
Words
8 (Address + 7)
9 (Address + 8)
10, 11
(Address + 9.
Address +
10)
PID Built-in Function Block
Parameter/Description
PID_IND: Integral Rate (Ki)
PID_ISA: Integral Rate (1/Ti = Ki)
PID_IND: Rate of change in the Control Variable
in CV Counts per second when the Error is a
constant 1 PV Count. Entered as an integer
representing a fixed-point decimal rate with
three decimal places. The least significant digit
represents 0.001 counts per second, or 1 count
per 0.001 second. Displayed as Repeats/Sec
with three decimal places.
For example, Ki entered as 1400 is displayed as
1.400 Repeats/Sec and results in a Ki * Error * dt
or 1400 *
20 * 50/1000 = 1,400 contribution to PID
Output for an Error of 20 PV Counts and a 50 ms.
CPU sweep time (Sample Period of 0).
PID_ISA: The ISA Integral Time in seconds, Ti,
must be inverted and entered, as integral rate,
as described for PID_IND. Total integral
contribution to PID Output is Kc * Ki * Error * dt.
Ki is usually the second gain set after Kp.
CV Bias/Output Offset
Number of CV Counts added to the PID Output
before the rate and amplitude clamps. It can be
used to set non-zero CV values when only Kp
Proportional gains are used, or for feed-forward
control of this PID loop output from another
control loop.
CV Upper Clamp
CV Lower Clamp
Number of CV Counts that define the highest
and lowest value that CV is allowed to take.
These values are required. The Upper Clamp
must have a more positive value than the Lower
Clamp, or the PID block will not work. These are
usually used to define limits based on physical
limits for a CV output. They are also used to scale
the Bar Graph display for CV. The PID block has
anti-reset-windup, controlled by bit 4 of the
Config Word, to modify the integral term value
when a CV clamp is reached.
Chapter 14
Jan 2020
Low Bit
Range
Units
Repeats/
0 to 32.767
repeats/sec
0.001 Sec.
CV Counts
-32768 to
32767
(add to PID
output)
CV Counts
-32768 to
32767
(Word 10
must be
greater than
word 11.)
254
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