WATLOW Series 988 User’s Manual 7.1
Tuning, Manual Operation, Alarms and Error Codes, Chapter 7
Auto-tuning (Heat and/or Cool)
The Series 988 can automatically tune the PID parameters to fit the char-
acteristics of your particular thermal system.
Standard software units
(98_ A -_ _ _ _-_ _ _ _)
have 1 set of PID parame-
ters. Units with enhanced software (
98_ B -_ _ _ _-_ _ _ _)
and [AlgO] set
to [Pid2] (Global Menu) have two sets of PID parameters, PID A and PID
B. Only one PID set can be auto-tuned at a time. For information on tun-
ing a cascade system, see Chapter 8.
Before beginning the auto-tune sequence, make sure the [AtSP] parame-
ter located in the Global Menu is at the proper setting. This allows the
user to select the tuning set point as a percentage of the current control
set point. See Chapter 4 for more information on this parameter. The fig-
ure below uses the default setting, 90%, to define the auto-tuning process.
Once the auto-tune sequence has begun, the output 1 and output 2 pro-
portional band is set to 0 and the control goes into an on/off mode of con-
trol at the set point percentage determined by the [AtSP] parameter. The
displayed set point remains unchanged.
