Watlow Electric SERIES 980/985 Benutzerhandbuch

Chapter 5

How to Tune and Operate

Auto-tuning: The Series 9801985 gives you the capability to automatically tune
the PlD parameters to fit the characteristics of your particular thermal system.

The auto-tuning procedure operates on a thermal  response value - slow,

medium, or fast. A slow thermal response is used when the process  tempera-

ture is not met too rapidly, or greatly exceeds the set point value. A fast thermal

response produces a rapid temperature change over a short period of time.

Once the auto-tune sequence has begun, all  PID values for both heat and cool

are set to 0 and the control goes into an ON/OFF mode of control at 90% of the
established set point. The displayed set point remains unchanged.

The cool output remains off for the duration of the tuning. Once the control has
finished “learning” the system, it returns to standard  PID control with the heat

PID values being automatically established as a result of the auto-tuning. The

operator must then establish the cool  PID values manually. Tuning is complete

within 40 minutes. Any change of the set point, while in auto-tune,  re-initiates
the auto-tune procedure.

1.

2.

3.

4.

Press the MODE key until the AUt prompt appears in the data display.

Select a thermal response value,  1=slow, 2=medium, and 3=fast, using
the UP/DOWN keys. A thermal response value of  2 will satisfactorily tune

most thermal systems.

Press the MODE key.  While the control is in the tuning mode, the lower

display alternately displays the normal information and the prompt      At. The
time between alternations is 1 second.

When the process is complete, the displays return to their previous state
and AUt reverts to 0. The appropriate PID tuning parameters are now

installed, and retained in the non-volatile memory.

To abort auto-tuning, the operator must reset the AUt parameter to 0. This

leaves the unit in an ON/OFF heat control state in Auto operation at the dis-
played set point. The auto-tuning process may also be aborted by pressing the
AUTO/MANUAL key twice. In both cases, all  PID values are set to  0.