Operating Instructions
(with some overshoot) reduce rate time 10-20%. For more anticipation (giving
undershoot) increase rate slightly. Experiment with (HG) settings.
EXAMPLES OF PARAMETER SETTING ON TWO PROCESSES
Process A: Slow, 2 lag process, matched power, 200º set point.
HG
RT
TEMPERATURE
REMARKS
409 00 197º-199º Process shows 2º oscillation, 2º average droop -
cut gain setting in half.
200 00 196º
200 05
200 10
200 20
200 40
194º-206º
199º-201º
200º
198º-202º
Process is stable, Gain O.K. but 4º droop-requires
addition of rate-add 05 for slow process.
Process shows 8º slowing oscillation, reset is
hunting, double RT to 10.
Almost -double RT value again.
Good-process is stable. Double again to see if we
can improve.
Now process is showing 4º faster (rate) "hunting”.
Back up again. RT = 20.
Process B: Fast, 3 lag, overpowered process, 400° set point.
HG
RT
TEMPERATURE
REMARKS
409 00 389º-435º
25 00
375º-391
12
00
384º
12 01
371º-435º
12
02
396º-404º
12
03
400º ±
12
04
400º
Process
oscillates,
wild, skip to much less gain.
With 16º oscillation, 17º droop- galn should be cut
Gain O.K., 36º droop- now add
RT
=
1 for fast
process.
Need more rate tlme-double to 2.
Getting
close-add a little more.
Good-add a
little
more to see if we can
improve.
Optimum
Low gain requirement
indicates
poor thermal
coupling
or overpower.
Special
problems can be caused by very noisy
by systems havlng a pure dead time between
turbulent flow processes or
heat application and
temperature measurement. In both cases, rate is
likely to continuously
overreact. Unplug unit and set internal switch to reduced rate gain. (From
back of case, your left,
B-2,
top position).
Cool Gain
If
cooling
is to be controlled, first
optimize
the heat
(CG)
Setting
adjustments. Start heat generating mechanism
(chemical reaction,
mechanical,
subambient set
point,
etc. that will require cooling action.
Set cool
gain
to 400 (maximum). If stable, enter.
Most likely the temperature will oscillate. Record
I
1.
2.
3.
Z:
values used.
Reduce gain to 200. Compare temperature
oscillations. If oscillations are reduced, continue
lowering gain until process is stable.
If up and down temperature peaks get bigger, cool
cycling (CC) may be too long or the cooling
mechanism has too much lag or time delay. If
possible, improve dynamics of cool transfer, If not,
go to rate (RT) and double rate time.
4. Now optimize cooling gain as in step 2.
5. Since heat rate will now be too long, cut heat gain
15
in half.
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