Watlow CPC400 - Manual (Page 76)

Chapter 3: Operation and Setup CPC400 Series User’s Guide
62 Watlow Anafaze Doc. 0600-2900-2000
Table 3.8 Scaling Values
Autotuning
Autotuning with TRU-TUNE+™ adaptive control is a pro-
cess by which the CPC400 controller calculates the PID pa-
rameters for optimum control. Both heating and cooling
PID parameters are set.
The preferred and quickest method for tuning a loop is to
use the tune mode to establish initial control settings and
continue with the adaptive mode to fine tune the settings.
Setting a loop’s control mode to tune starts this two-step
tuning function. First a predictive tune determines initial,
rough settings for the PID parameters. Second the loop au-
tomatically switches to the adaptive mode which fine tunes
the PID parameters. This function can be used for heat-
only, heat and cool, and cool-only PID control systems.
Once the process variable has been at set point for a suit-
able period of time (about 30 minutes for a fast process to
roughly 2 hours for a slower process) and if no further tun-
ing of the PID parameters is desired or needed, the control
mode may be switched to auto. However, only operating the
controller in the adaptive mode allows it to automatically
adjust to load changes and compensate for differing control
characteristics at various set points for processes that are
not entirely linear.
Once the PID parameters have been set by the TRU-
TUNE+™ adaptive algorithm, the process, if shut down for
any reason, can be restarted in the adaptive control mode.
Before Tuning
Before autotuning, the controller hardware must be in-
stalled correctly, and these basic configuration parameters
must be set:
• Input type (and scaling, if required)
• Output type (and scaling, if required)
Parameter Value
Input range high 11.111 FPM
Input high signal 2000 Hz
Input range low 0.000 FPM
Input low signal 0 Hz
2000 pulses
1 second
--------------------------------x
60 seconds
1 minute
-------------------------------x
1 inch
900 pulses
-----------------------------x
1 foot
12 inches
-------------------------- 11.111 FPM =