This instrument is compatible with four standards of site to measure surface roughness of various machinery-processed parts, calculate corresponding and clearly display all measurement parameter. When measuring the roughness of a surface, the sensor is placed on the surface and then uniformly slides along the surface by driving the mechanism by the sharp built-in probe. This roughness causes displacement of the probe which results in change of Inductive amount of induction coils so as to generate analogue signal, which is in proportion to the surface roughness at output end of phase-sensitive rectifier. The exclusive dsp processes and calculates and then Outputs the measurement results on lcd. * multiple parameter measurement: ra, rz, rq, rt * highly sophisticated inductance sensor * four wave filtering methods : rc, pc-rc, Gauss and d-p * built-in lithium ion chargeable battery and control Circuit with high capacity * small in size, light in weight and easy to use * can communicate with pc computer for statistics, Print and analyz by the optional cable and the Software for rs232c interface. *manual or automatic shut down. The tester can be Switched off by pressing the power key at any time. On the other hand, the tester will power itself off About 5 minutes after the last key operation.