In the production field of the automobile industry，it is strongly needed a small sized instrument for measuring the roughness of the deep hole surface. This small sized instrument must have these functions: the automatic measurement for multiple points

the complicated data disposal ability

the good quality for graphics display

and sometimes

the rewrite permissibility of the control program to fit different workpiece. The instrument with so many functions made in past

each one have large size and were rather difficult to be used in production field. An effective compact design for the instrument has been realized with the common PC to be replaced by the ARM920T Circuit Block

one type of embedded system. The new developed instrument have not only all of the functions mentioned above but also the advantages such as low cast

high reliability

and especially the small-size. Most of details are introduced these are the integrated design of the measuring instrument

the interface circuit of the embedded system

the general parameter arithmetic for multiple points etc. The new developed instrument can be used to measure the roughness on the inner surface of a hole it’s aperture size is 16~25mm and it’s length is 120~180mm. The measured generatrixs may up to 32 and the points 512. According to the practice use test

the maximum measuring error is less than 5%

however

the new instrument is very adaptive for the industrial need