A sun following system was constructed and tested. The tracker gives the possibility for automatic measuring of direct solar radiation with a pyrheliometer. The mechanism is operated by a digital program in the control system, situated separately from the mechanical part. The position of the sun is calculated. and the pointing errors appearing during its daily work are stored for later analysis. Additionally. in the active operation mode, the tracker uses the signal of a sun detecting linear sensor to control the pointing. Two AA stepper motors move the instrument platform, keeping the sun's beam at the center of the sensor. The mechanism was created at the Laboratory "Evaluation Solar" of the Technical University Federico Santa Maria (UTFSM) in Valparaiso, Chile. The experiments show good results. The described sun tracker gives similar results as the Swiss sun tracker INTRA at a very much lower price. (C) 2004 Elsevier Ltd. All rights reserved.