Research On The Technology Of Siganl Conditioning And Digital Filtering Of Profilometer

Surface roughness is an important plant of work piece, and it will directly affects the performances such as coefficient of friction, anti-fatigue, performance, and so on, so, as an important instrument for measuring surface roughness, profilometer is widely used in machine tools, automobiles, instrumentation and other industries. The performance of profilometer mostly depends on the precision of measurement, which is absolutely determined by the performance of signal conditioning circuit and digital filter. Referring to great lot of scientific and technical literatures which are relevant with surface roughness measurement, this dissertation, firstly analyzes the present condition of roughness measurement techniques domestically and abroad, on this basis, signal conditioning circuit and digital filters are developed, and applied to the process of the transformation of Talysurf5 type profilometer.This dissertation analyzes the function and structure of signal conditioning circuit, and develops sine wave oscillating circuit, AC amplification circuit, band pass filter circuit, range switching circuit, phase sensitive detection circuit and a low pass filter circuit. Develops analog-digital conversion circuit and high-precision reference voltage circuit. This dissertation also analyzes the anti-jamming principium of photocoupler, and uses photocoupler to isolate the analog part of signal conditioning circuit from the digital part.This dissertation derives the filtering equations of 2RC filter, phase-correct filter, and Gaussian filter from corresponding digital filtering principles, and also implements these three digital filters in software. According to the definitions on roughness evaluation parameters of national standard GB/T 3505-2009, this dissertation derives the process of calculating main roughness evaluation parameters. Develops surface roughness evaluation software based on VB and VC. Applies both the signal conditioning circuit and this software to the transformation process of Talysurf5 type profilometer, and calibrates it.