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Diplomarbeit 2004 (DA04): Arbeits-Archiv
 
DA Bhi 04/1 - Light control with reflectormeter
Studierende: Martin Scheu, scheumar
  Urs Weber, weberurs

Betreuer: Roland Büchi, bhir

The aim of this project was to measure the illumination on a remote table top independent from the colour of its surface. In view of the fact that the brightness depends on the reflection coefficient of the surface, the identification of the reflectance was the main point of this degree dissertation. After a period of making oneself thoroughly acquainted with the theory of reflectance we first had to realise the proposals of solution of the previous project work. Amongst other things, the replacement of the used sensor elements was made. Said project work already dealt with the measuring of the illuminance of remote objects, however with consistent colour of surface. As an answer to the problem of the measurement of reflectance we elaborate the pulsed sending such as the aimed reception of an invisible signal. By means of change of amplitude of pulse the reflectance can be concluded.

As this measurement is made over a large distance the application of powerful transmitters and highly sensitive receivers is required. But even those elements must be operated within their threshold which leads to the fact that they are very susceptible to external influence. These influences are very distinctive when being optically applied and change continuously, so they cannot be eliminated by means of simple compensations.

In order to confirm the principle of measurement of reflectance despite of the strong annoyances, the height of measurement was defined to 1m. The signal processing and linkage of the sensor information took place with xPC-Target, a subprogram from Matlab. As a result of the low sampling rate of this system additional analog circuits are necessary. This project points out that the measurement of the illuminance with the required consideration of reflectance can be successfully realised by choosing the appropriate components and interpretation of the available sensor dates.

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