Where the Heat Comes From

Any electrical or mechanical equipment may intentionally or unintentionally generate heat when it is operating. This heat radiates from the surface of the equipment and is the basis of the thermal images we observe. While Thermographers sometimes measure absolute temperatures, they generally use relative temperature differences as a more appropriate indicator when identifying or describing anomalies.

• Elevated temperatures in electrical equipment may mean an overloaded circuit, corroded or loose connections, deteriorating components, induction from eddy currents, high neutral currents or phasing problems etc.

• Lowered temperatures on the other hand may be due to things such as open circuits, operational failures or load imbalances.

• Actual temperatures are important in production work, manufacturing industries, cold storage, laboratory work, etc. Thermography is generally not a routine issue in these cases (other methods of temperature monitoring, and sometimes fixed thermal imagers are more common).

Although an elevated temperature may be generated deep within a component, it is only the heat being radiated from the surface of the object that is detected. Keep this in mind - the temperature deeper within the object can be much higher than the surface. Thermal imaging therefore does NOT see through walls, panel covers, nor most other solid objects. At the wavelengths normally used both silica glass and clear plastics are opaque.

To further complicate things the surface property of emissivity can greatly affect the "apparent" surface temperature on different objects.