Watlow Series 988 Enhanced Manuel d'utilisateur télécharger pdf (Page 10)

10 WATLOW Series 988 Enhanced Software Features

Sample Application

A test engineer needs to control the temperature in a test chamber that

can be operated at normal atmosphere or under vacuum conditions. If he

tunes the controller for normal atmospheric conditions, when he reaches

the portion of his test that requires a vacuum, he must stop the test and

enter new PID parameters to maintain stable temperatures. The system

characteristics are so very different, that one set of PIDs will not give satis-

factory results under both normal and vacuum conditions.

The Series 988 solves this problem with the dual PID option. Auto-tuning

PID A under normal atmospheric conditions, then auto-tuning PID B

under vacuum conditions, establishes PID values for two sets of system

characteristics. A pressure switch connected to the event input tells the

controller when to switch between PID A and PID B, eliminating the need

to change PID values manually.

Figure 9.10 - Test

chamber controlled

with dual PID sets.

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Watlow Series 988 Enhanced Manuel d'utilisateur Page 10