Watlow Series 96 - Manual (Page 21)

Wa t l o w S e r i e s 9 6 F e a t u r e s ■ 5 . 2
Auto-tune
Auto-tuning allows the controller to explore the
responsiveness of the system to determine an effec-
tive set of parameters for PID control. To do this it
crosses an auto-tune set point several times, then
controls at the normal set point using the new
parameters.
Use Auto-tune Set Point [AtSP] (User Menu) to
select the temporary set point, as a percentage of the
normal set point, that the controller will tune to.
Initiate or cancel the auto-tune process with Initiate
Auto-tune [`Aut] (User Menu).
In heat-only or cool-only modes the only option is
[tune].
In heat/cool or cool/heat modes there are three tun-
ing options:
[tune] tunes both heat and cool at the same time.
This is appropriate if the system typically operates
with both heat and cool contributing, such as in an
environmental chamber.
[PiD1] tunes just PID set 1. This is appropriate for
tuning the heat of an extruder application in the
endothermic mode.
[PiD2] tunes just PID set 2. This is appropriate for
tuning the cool set of an extruder application in the
exothermic mode.
Figure 5.2a Auto-tuning.
CAUTION: Choose an auto-tune set point value that will pro-
tect your product from possible damage from overshoot or
undershoot during the auto-tuning oscillations. If the prod-
uct is sensitive, carefully select the auto-tune set point to
prevent product damage.
Temperature
Auto-tune begins
Auto-tune Set Point
(default 90 percent of Process Set Point)
Auto-tune complete
Power Limit
A high side power limit and low side power limit set
the maximum output power within two ranges.
A low side power limit limits the output to a per-
centage of the maximum output power while the
process temperature or value is below the power
limit set point.
The high side power limit limits the output to a per-
centage of the maximum output power while the
process temperature or value is above the power
limit set point.
The power limits work the same way in a cooling
applications, but the negative values are converted
to absolute (positive) values for determining whether
the range is below or above the power limit set
point.
The low side power limit can be viewed or changed
with High Power Limit Below [Pl`B] (Global
Menu).
The high side power limit can be viewed or changed
with High Power Limit Above [Pl`A] (Global
Menu).
The power limit set point can be viewed or changed
with Power Limit Set Point [PLSP] (Global Menu).
The actual output power can be viewed with Percent
Output [Pcnt] (Monitor Menu).
Figure 5.2b Power limits.
Time
Temperature
Process Temperature
Range High
Range Low
Power Limit Set Point
(between Range Low and Range High)
Output Power is limited to
Low Side Power Limit
Output Power switches
to High Side Power Limit
Output Power is limited to
High Side Power Limit