Surface quality is checked by physically running a fine diamond stylus over the surface and recording how much it rises and falls as it crosses the peaks and valleys. This movement is converted into an electrical signal and processed into roughness values such as \( R_a \). A clinometer, a sine bar, and an autocollimator are all used to measure angles or check flatness and straightness using gravity or light, none of them drag a stylus across the part. The instrument built specifically to trace a surface with a stylus and report its roughness profile is the profilometer, which is what the question calls a profile meter.