Surface Roughness Tester Dealer In Ahmedabad. A roughness tester is used to quickly and accurately determine the surface texture or surface roughness of a material. A roughness tester shows the measured roughness depth (Rz) as well as the mean roughness value (Ra) in micrometers or microns (µm). Typical roughness testers provide a linear roughness measurement, tracing a mechanical tip along a surface to measure roughness along an arbitrary line. More sophisticated versions provide an areal roughness measurement, which measures an area of the surface using non-contact methods, such as lasers, optics, interferometers, and more, to give finer resolution and wide area measurements. For this discussion we will focus on portable roughness testers and linear roughness measurement. Roughness values are typically reported in Ra, which is the average absolute deviation from a central line of a surface; Rq, which is the root mean square of the deviation, and numerous other values that measure peak heights and depths of valleys. For most applications Ra and Rq provide an adequate indication. For specially designed surfaces, the other parameters may be more appropriate.