Methods and Devices of Processing Signals of Optoelectronic Position Transducers

Abstract

1.1 Precise optoelectronic position transducers In digital position measurements two opposite ideas of taking measurements can be observed. They both tend towards obtaining the most precise results. The first idea is based on the precise construction of the glass scale and construction of the optoelectronic transducer by using simple circuits of electronic processing. The second idea is based opposite, that is on precise circuits of electronic processing and simple construction of the glass scale and construction of the optoelectronic transducer. The position transducers can be classified as quantizing (dynamic) and coding (static). The quantization transducers produce an electric impulse during shift of length or angle unit in a way that on the output of the transducer the number of impulses proportional to measured value is obtained. The coding transducers are used to make a conversion from linear or angular displacement to a number code. About measurement accuracy of optoelectronic transducers decides first of all value of discretisation error which depends on number of modulation elements, fall to number of linear or angular shift unit. Among the new optoelectronic transducers, the width of gaps modulating beam of light reaches value of 0,05..0,004 mm. It enables to construct the transducer of resolution 10000 grains per rotation at disc diameter varies from 25 to 320 mm (discretisation error 0,01%) (Heidenhein, 2003) (Holejko, 1981). In cases where specific work conditions exist (high dustiness, high temperature) the optoelectronic transducers cannot be used. In such cases special very precise magnetization scales are used (Heidenhein, 2003) (thin layers range micrometers – elements of different residual magnetism placed alternately)