Measuring transistor temperatures with an ear thermometer

[Solder_Junkie]

Further to my earlier question regarding measuring transistor tempertures with an ir thermometer, Sean replied with a suggestion of using a cheap domestic ear thermometer. Most of these only read temperatures a few degrees either side of body temperature and outside that range show Hi or Lo... Which isn't much use for other purposes. However, they have a very small (3mm or so) sensor and a narrow probe.

The "Ezi" range of thermometers have an "Object" measuring range going from 0 - 100 deg C and are very cheap, less than 10 GBP delivered on eBay.co.uk. The object range is enabled by fitting a front cover, which operates a plunger switch to change the range. The switch is easily glued down allowing the use of the narrow probe without the wide cover, which can be placed close to small components such as TO92 sized transistors.

Very useful and a lot cheaper than a thermal camera for hobby use.

[SeanB]

Just keep a black dry wipe marker with it, so that you can make a black target on shiny surfaces like aluminium or metal cans, so that the thermometer will read the IR emission of the actual object instead of whatever is reflected off the shiny surface. Makes a big difference, uswe on ewvery part to ensure that the emissivity to the sensor is constant, instead of varying wildly.

https://en.wikipedia.org/wiki/Thermography#Emissivity

https://en.wikipedia.org/wiki/Emissivity

A little explanation and a rough table for most common materials.