The study of thermal control in different geometry cavities (cylindrical and rectangular), to obtain high accuracy, short and long term stability responses applied to electronic instruments, is presented. Automatic dynamic electrical compensation is achieved by a feedback electronic circuit and low thermal inertia sensors. One sensor element is also employed as an actuator (heat generator) and the other as a reference sensor (resistance of manganine wire). In the rectangular cavity, the transducer (that is sensor and heater) is manufactured directly in the circuit board surface using a CAD/CAM equipment. This architecture allows a high dimensional accuracy of the sensor/actuator with a minimum track thickness, i.e., around 100 μm. In the cylindrical cavity, the transducer is manufactured using a copper wire. For this geometry, low aspect ratios were analyzed. Electronic response equations are derived and coupled to those governing the heat transfer phenomenon in cavities. After several tests, the model is compared to the experimental data. The obtained results seem to confirm the validity of the proposed idea, allowing an accurate temperature control in cavities with a self calibrating feature. At present time, we have obtained for both geometries a precision around of 0.01 oC and an accuracy around of 0.1 oC.
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