Vishay thermal EMF video

Vishay has released a video that demonstrates the thermal EMF characteristics of four resistor technologies: thin film, thick film, metal strip and bulk metal foil.

The short video demonstrates how a slight temperature rise can introduce thermal EMF error voltages in the thin film, thick film and metal strip resistors, but causes practically zero thermal EMF error in the bulk metal foil resistor.

Electronic components, and resistors in particular, incorporate dissimilar metals in their construction. When one of the two junctions of dissimilar metals is heated, a voltage is generated between the two junctions. This is known as the Seebeck or thermocouple effect and it occurs in resistors at the device's two element/termination junctions.

When heat is applied to either junction, the error voltage increase is directly proportional to the temperature increase. This is called thermal EMF and it can be a very big problem in applications where it is necessary to make accurate, low-level circuit measurements.