The deep groove sensor of Mitech portable surface roughness tester MR200, with totally length of 80.5mm, main body length of 46mm, guide-head bearer length of 23mm, main body diameter of Φ10mm, core-insert sleeve diameter of Φ7mm, guide-head height of 14.2mm, It is the optional configuration of the surface roughness tester, mainly used for measuring the roughness for various surfaces like plane, inclined plane, cone, inner hold and grooves. The deep groove sensor is closest to the standard sensor, only larger its depth. Compared with the standard sensor, it is not able to carry on the handheld measurement. It needs to work with the measuring platform, mainly for measuring the roughness of the workpeice with the depth which the standard sensor can’t reach.