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Sensor catalog - 7347 GeneralInformation

Application Hints

Sensor in a Static System Sensor in a Dynamic System Sensor in a Combination Static/Dynamic System the system is static, placing the sen-sor closer to the heat source willkeep the heat fairly constant throughout the process. In this typeof system the distance between theheat source and the sensor is small (minimal thermal lag); therefore, theheat source will cyclefrequently,reducing the potential for overshootand undershoot at the work load.With the sensor placed at or nearthe heat source, it can quickly sense temperature changes, thus maintain- ing tight control. When the heat demand fluctuates and creates a system between staticand dynamic, place the sensor half- way between the heat source andwork load to divide the heat transferlag times equally. Because the sys-tem can produce some overshoot and/or undershoot, we recommendthe electronic controller selected forthis situation include the PID features(anticipation and offset ability) to compensate for these conditions.This sensor location is most practicalin the majority of thermal systems. the controller to take the appropriateoutput action more quickly. However, in this type of system the distance between the heat source and the sensor is notable, causing thermal lag or delay. Therefore, the heat source cycles will be longer, causing a wider swing between the maximum (overshoot) and minimum (undershoot) temperatures at the work load.We recommend that the electroniccontroller selected for this situationinclude the PID features (anticipationand offset ability) to compensate forthese conditions. With the sensor at or near the work load, it can quicklysense temperature rises and falls.
General Information

Where should my sensor be placed?

LoadSensorHeater Application Hints Placement of the sensor inrelationship to the work load and heat source can compensate for various types of energy demandsfromthe work load. Sensor placement can limit the effects ofthermal lags in the heat transferprocess. The controller can only respond to the temperature changesit “sees” through feedback from thesensor location. Thus, sensorplacement will influence the ability ofthe controller to regulate the temper- ature about a desired set point.Be aware sensor placement cannotcompensate for inefficiencies in thesystem caused by long delays inthermal transfer. Realize also that inside most thermal systems, temperature will vary from point-to-point. We call a system “static” when thereis slow thermal response from the heat source, slow thermal transfer and min- imal changes in the work load. When We call a system “dynamic” whenthere is rapid thermal response fromthe heat source, rapid thermal transfer and frequent changes in the work load.When the system is dynamic, placing the sensor closer to the work load will enable the sensor to “see” the load temperature change faster, and allow
LoadSensorHeater LoadSensorHeater 25