Sleep and Sensory Analysis Group - Sensing everything between heaven and earth
Sleep and Sensory Signal Analysis Group

Examples of our studies

Sleep analysis
Epilepsy analysis
Measurement chair
Sensing the human
Tablet interface
Other user interface studies
Engine signal processing
Health informatics standardisation
Secret company projects
Ancient web history

Doctoral theses

Tablet interface

Measuring the accuracy of the tablet interface
A reasearcher is measuring the positioning accuracy of the unconventional tablet.
  Robust user interaction to computers

Some applications require a vandal resistant user interface to an embedded computer system. A plate of steel with shock resistant sensors is as robust as one can imagine.

The principle of this tablet like sensor is rather simple: a rigid rectangular plate has four sensors under it, one in each corner. When the user presses a point in the visible area of the plate, the pressure is divided unevenly among the corner sensors and the position of the pressing can be calculated from the measured pressure values. The calculation formula is rather simple but practice showed that it does not give accurate results right away. Therefore we needed to derive a correction formula which significantly improved the localisation accuracy of the pressings. The final location error with the prototype in the picture is on the average 1.8 mm.

A similar input device, brand named VISSUMO (previously Infini Touch) was developed independently by QSI Corporation, USA. Their web pages and their US patent application US 2006/0279553 A1 describe more details about the principles of this technology.

This study was conducted in co-operation with VTT Technical Research Centre of Finland, Department of Automation Science and Engineering in Tampere University of Technology and the TAUCHI research group in Tampere University.

Emfit Ltd. EMFI sensors
Our paper about the tablet in IEEE Explore
E-mail to Alpo.Varri (at)
Designed by Alpo Värri 28.1.2013
Department of Signal Processing Tampere University of Technology
P.O. Box 553, FI-33101 Tampere, Finland, Tel. +358-40-8490780
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