How much of a surface do you need to measure in order to accurately describe its roughness? For typical surfaces, the standards suggest an evaluation length 5 times longer than the roughness cutoff. But if you are measuring a narrow feature or part, the entire surface may be smaller than that 5X length.

In this video we show you how to determine the “evaluation length” for measuring roughness on a typical surfaces, and we introduce options for measuring texture on smaller surfaces. We also point out some pitfalls that can lead to incorrect evaluation of roughness and waviness.