HOW TO MEASURE

Assume that I have convinced you that the approach makes sense. Before deciding which measuring method to use, you need to consider the technique’s basic requirements.

The construction of the heating elements usually resembles wire-wound resistors. To pack long enough wire into a small space, the wire is wound into a coil that’s mechanically supported by a piece of nonconductive material. This means that the element has considerable inductance and the measurement technique needs to ensure that the inductance of the element is distinguished from its resistance. This is important because surrounding objects may influence the inductance. Changes in such interference would lead to incorrect variations in the measurement results.

The heating element is connected to the power source by cabling (with or without connectors). It’s important to make sure that changes in the cable/connector resistance aren’t taken into account.

Power dissipation in the element during measurement needs to be low compared to the thermal resistance between the element and the heated medium. Otherwise, a significant difference in temperature would develop between the two and the measurement would be inaccurate.