I've tested a lot of thermal cameras, and this tiny one is a new favorite

Regular readers will know that I am a big fan of thermal cameras. They are cool and give you a view of the world you can't otherwise see, but they are also super useful and have become a key tool in my repair toolbox. I've used them for everything from spotting a faulty component on a circuit board to finding a wiring problem underneath floorboards.

A thermal camera is a super useful tool -- and these devices are cheaper than you might think.

Also: Want an entire tech repair shop of tools in a single messenger bag? iFixit can fix that

The Thermal Master P2 thermal camera, which the manufacturer says is the "world's 2nd smallest thermal camera", is the perfect tool for the engineer, mechanic, or handyperson on the move.

Thermal Master P2 tech specs

Resolution: 256 x 192 (512 x 384)Temp range: -20°C to 550°CRefresh rate: 25HzZoom: x15Accuracy: ±1.5℃Temperature resolution: 0.04℃Weight: 10gPower consumption: 0.3WConnector: USB-CCompatibility: Android (not compatible with iPhones or iPads with USB-C)

Getting started with the P2 is easy. Download and install the Temp Master app from the Google Play Store, fire up the app, pop the camera into the USB-C port, and away you go. 

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If your Android smartphone is the ruggedized type, you might have problems fitting the camera, meaning you'll need to use the supplied USB-C extension cable.

Also: This tiny USB-C accessory has a game-changing magnetic feature (and it's 30% off)

The camera is tiny, weighing about 10 grams, and it fits into a carry case that is small enough to hook onto a keychain, so it's always ready when you need it.

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I've used many thermal cameras and one P2 feature I like is the 25Hz refresh rate. It makes my thermal cameras with slower refresh rates feel slow and clunky by comparison. I also like how the 15x zoom lets me get close to the action.

Also: I tested the world's first thermal phone camera with a 50Hz refresh rate, and here are the results

The temperature resolution is sensitive -- more than sensitive enough to "see" someone breathing by the temperature changes around their nose.

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Not sure what you can do with one of these thermal cameras? Here are just a few things you can do:

Find overheating electrical components (faulty components usually run hotter)Diagnose all sorts of HVAC problems, from windows that leak heat to radiators that aren't warming up properly to AC units that aren't coolingFind dangerously overheating rechargeable batteriesFind radiator pipes underneath floorboardsFind overheating power cablesFind problems with cooling systems on desktop and laptop systemsSpot binding brakes on cars

Here is a picture of a USB-C cable getting warm when carrying a heavy current load:

Adrian Kingsley-Hughes/ZDNET

My tip for learning to use a thermal camera is to use it to look at things when they aren't faulty -- your radiators, car brakes, electrical stuff, anything -- and get to know how things should look, so you can tell when things aren't working right.

ZDNET's buying advice

The Thermal Master P2 is a great thermal camera, and right now it's $50 off, bringing the price down to a very reasonable $199. It's a fantastic addition to any repair toolkit. I like the fast refresh rate and accuracy. However, this camera won't work if you shift to an iPhone despite having a USB-C port.