Measurement principles and methods

Either contact or non‑contact methods can be used. Contact methods include employing a surface roughness tester, whose built‑in sharp stylus slides over the surface being measured, senses its roughness, converts the displacement signal into an electrical signal, and ultimately outputs a roughness value. Non‑contact methods rely on optical principles—such as laser scattering and white‑light interferometry—assessing roughness by measuring the reflection or scattering characteristics of light on the coating surface.

Measurement parameters

Sa (Arithmetic Mean Height): a surface‑roughness parameter representing the arithmetic average of height deviations across the surface. A smaller Sa value indicates a smoother surface.

Sq (Root Mean Square Height): another common surface‑roughness parameter that represents the root‑mean‑square value of height deviations across the surface. Sq provides a standard‑deviation measure of roughness; a smaller Sq value indicates less variation in surface roughness.

Sz (Maximum Height): the maximum distance from the highest peak to the lowest valley in surface‑roughness measurement. Sz represents an extreme value, reflecting the greatest peak‑to‑valley difference on the surface.