Athena 6075 series, Instruction Manual, Page: 28 / 39

4. Press STAND-BY again and temperature will begin to rise. When the pro-
cess rises to the desired set point it will probably oscillate. Periodically
decrease the Gain (lower the HG number) until a small constant oscilla-
tion is obtained. Reducing the Gain by steps of one half (1/2) the previous
-HG- setting is an acceptable method to obtain the desired small oscilla-
tion. Note time between oscillations in seconds (“T” on Figure 5.3).
5. Decrease the Heat Gain to 60% of the value obtained in the previous step.
The Gain is now tuned. Enter the same number in the Cool Gain.
6. The best rate time (-RT-) setting is one-eighth ( 1/8) the time in seconds of
one cycle (see cycle time "T" in Figure 5.3). This will give a conservatively
tuned system. If faster response and/or faster rise to set point is desired
one-twelth (1 /12) of "T" may be used. Note that faster settings may yield
instability and temperature overshoots on startup. Remember that the
reset automatically tracks the rate (-rt-) adjustment
7. Connect cooling apparatus Observe control stability.
8. If oscillation occurs lower the cool gain number. If cooling is sluggish
raise the cooling gain number.
NOTE: In order to observe changes in process temperature, especially as
they relate to time, it is helpful to use a temperature recorder in conjunction
with all tuning and parameter setting procedures.
TUNING HINTS
1. Once the optimum -rt- and -HG- have been set into the unit, cold start tests
of the process should be tried. Remember that start-up and running
parameters will usually be different and it is desirable to adjust both gain
(HG) and rate/reset (RT) ±25% to strike a balance between good startup
and running settings.
Generally higher settings of -rt- will give more controlled start-ups with
less overshoot lower values will give faster recovery from process upsets
Higher gain settings will give tighter control of the running process. but
may give more overshoot on start-up.
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