Surface SURFACE THERMOMETERS Tel-Tru Surface Thermometers are designed to measure surface temperatures on a wide variety of surfaces and are available in several configurations.Surface Thermometers that Tel-Tru offers include:Dual Magnet Thermometers: Specifically designed to be used on horizontal or ferrous non-horizontal surfaces.Tab Thermometers: Designed with two tabs with pre-drilled holes for screws.Clip-on Pipe Thermometers: Used for temperature measurement on pipes or tubes.Spring Held Pipe Thermometers: Ideal for measuring surface temperatures of pipes, cylinders, and spindles. Clip-On Pipe Thermometers Dual Magnet Thermometers Spring Held Pipe Thermometers Tab Thermometers