Pre-Tuned Temperature Controllers

Several controller manufacturers supply temperature controllers where the parameters are factory-tuned and non-adjustable. The parameter settings are based on long-term experience with temperature controllers in extrusion applications. This is possible because the thermal characteristics of most extruders are rather similar. Advantages of this approach are easier installation and less chance of controller tampering by unqualified personnel. 

Controllers with non-adjustable parameters are not well suited to extrusion operations where changes in temperature are very rapid (water cooling, blown film, etc.) or very slow combined with long dead times, as may occur in very large machines. Typical controller settings for pre-tuned controllers are shown in Table 4.6. 

In Table 4.6, Xp is the proportional band, t the reset (integrating) time constant, and ta the rate (derivative) time constant. 

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