Tachograph - The Analogue Tachograph

The Analogue Tachograph

Most tachographs produced prior to 1 May 2006 were of the analogue type. Later analogue tachograph head models are of a modular design, enabling the head to fit into a standard DIN slot in the vehicle dashboard. This would enable a relatively easy upgrade to the forthcoming digital models, that were manufactured to the same physical dimensions.

The analogue tachograph head uses styli to trace lines on a wax coated paper disc that rotates throughout the day, where one rotation encompasses a 24-hour period. If the disc is left in the head over 24 hours, a second trace will be written onto the first, and so on until the disc is removed. It is an infringement of EU Regulation 561/2006 to use a disc for a period longer than it is designed for. Multiple overlapping traces may still be deciphered in the speed and distance fields, but it is far more difficult for the activity field where one trace can easily be obliterated by another. Analogue tachograph heads provide no indication to the driver of the need to change the disc.

Analogue data is retrieved visually, and can be assisted by manual analysis tools. Analogue discs can also be electronically scanned and analysed by computer, although this analogue to digital conversion process still requires human expert interpretation for best results, due to imperfections in the source disc such as dirt and scratch marks in the wax surface that can be incorrectly read as trace marks.