Often used to heat oil and transmission fluid, these heaters attach to containers with flat metal surfaces for heating contents without direct contact. All automatically shut off if the heater temperature rises above the maximum heat output to prevent overheating.

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.

Probes with wire leads offer more flexibility than probes with connectors already attached because you can either wire them to a terminal block or add your own connector. For installation, note that the red wire is negative.

Spring-loaded probes help keep readings accurate by making sure the tip stays in constant contact with the surface you're measuring. These probes are manufactured to conform to ASTM E230 for accuracy. Accuracy is how far off the reported value is from the actual temperature.