Sdq is the Root Mean Square (RMS) Surface Slope comprising the surface, evaluated over all directions.
Sa = 80 nm, Sdq=11.0 deg.
Sa = 75 nm, Sdq=0.2 deg.
Sdq is a general measurement of the slopes which comprise the surface and may be used to differentiate surfaces with similar average roughness. Sa. Sdq may find application for sealing systems, surface cosmetic appearance and may be related to the degree of surface wetting by various fluids. Sdq is affected both by texture amplitude and spacing. Thus for a given Sa, a wider spaced texture may indicate a lower Sdq value than a surface with the same Sa but finer spaced features, as demonstrated above.