90 Degrees and Rising

It wasn’t just the temperature outside that rose significantly this summer @ Elektor House. While testing his prototype of the soon to be published battery testing circuit, lab worker Tim Uiterwijk was surprised to measure the temperature of a 7-watt series resistor at well over 90 ºC! This wasn’t expected, as the calculated dissipated energy (Pdiss) was well below the 7 W the power wire wound resistor is allowed to dissipate according to its specifications.