Surfaces are designed into products to reduce friction, “store” lubricants, provide a high luster finish or be the proper texture to hold paint (but not show the actual surface of the paint). The measurement of surface finish has come a long way in the past 70 years. It has advanced from fingernail scratch pads to microprocessor or PC-based systems with inductive probes. And today, there is an explosion of optical sensors to evaluate part surfaces with noncontact methods to levels unheard of in the past.
ISO processes require the documentation of surface finish quality and traceability of surface finish measuring instruments. The vast majority of surface texture checking systems are still the contact type with a very fine stylus being dragged over a part. That is why there is an increasing importance of calibration and certification for surface finish gages.