Often used where it’d be difficult to mount a standard probe, these probes stick onto magnetic surfaces to take temperature readings. They have a magnet that holds them firmly in place on motors, bearings, and other surfaces. A spring behind the probe protects the cable from strain that could cause it to fray or break. Pick the thermocouple type that best covers the temperature range you expect your surface to be. You should also make sure the thermocouple type you choose is compatible with the devices you plan to connect it to. They’re often used with temperature controllers, thermometers, and other temperature-reading devices.