A simple and low cost stylus profiler made of ferrite cores

Abstract

A new profile measuring instrument for measurement of variations at the sub-micrometre level is introduced. A variable-overlap-area-type inductive transducer is selected as a measuring transducer. It has a high sensitivity of 2289.70 mV V-1 mm(-1) and a high degree of linearity, with a maximum deviation of less than +/-0.075% in the range +/- 200 mum. The transducer is composed of ferrite cores which have good magnetic characteristics in spite of their low cost. The contact probe attached to four-bar spring maintains sufficient stiffness to isolate disturbances and transmits the profile information to the measuring transducer. The reproducibility of this proposed low cost profiler is better than 50 nm and its resolution is 5 nm at 1 mV noise level. Experimental results show that the proposed system can measure the three-dimensional profile of an object with sub-micrometre features.