Temperature Characteristics with On-Off Control

The approximate time/temperature characteristics of a simple on-off controller are relatively easy to visualize. If a dual output on-off control is considered, then a typical temperature/time curve can be shown as in Fig. 4.38. 

Typical temperature/time curve for a dual output on-off control 

If the system heats up from ambient temperature, the heating power will be turned off when the temperature reaches  

The temperature will continue to drop for a time period of t j. When the temperature drops below t, the heating is turned on again. After another time period of t, the temperature will start to increase again. This temperature cycle will repeat itself if the thermal conditions of the process remain the same. The maximum tempera- 

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