User manual

PID Loop Operation
(DL450 Only)
Maintenance
and Troubleshooting
8--56
PID Loop Operation (DL450 only)
DL405 User Manual, 4th Edition, Rev. A
Now that we have described the general ramp/soak generator operation, we list its
specific features:
S Each loop has its own ramp/soak generator (use is optional).
S You may specify up to eight ramp/soak steps (16 segments).
S The ramp soak generator can run anytime the PLC is in Run mode. Its
operation is independent of the loop mode (Manual or Auto).
S Ramp/soak real--time controls include Start, Hold, Resume, and Jog.
S Ramp/soak monitoring includes Profile Complete, Soak Deviation (SP
minus PV), and current ramp/soak step number.
The following figure shows a SP profile consisting of ramp/soak segment pairs. The
segments are individually numbered as steps from 1 to 16. The slope of each of the
ramp may be either increasing or decreasing. The ramp/soak generator
automatically knows whether to increase or decrease the SP based on the relative
values of a ramp’s end points. These values come from the ramp/soak table.
The parameters which define the ramp/soak
profile for a loop are in a ramp/soak table.
Each loop may have its own ramp/soak table,
but it is optional. Recall the Loop Parameter
table consists a 32--word block of memory for
each loop, and together they occupy one con-
tiguous memory area. However, the ramp/soak
table for a loop is individually located, because
it is optional for each loop. An address pointer
in location V+34 in loop table specifies the
starting location of the ramp/soak table.
In the example to the right, the loop parameter
tables for Loop #1 and #2 occupy contiguous
32--word blocks as shown. Each has a pointer
to its ramp/soak table, independently located
elsewhere in user V--memory. Of course, you
may locate all the tables in one group, as long
as they do not overlap.
Ramp/Soak Table