[Calibration of pressure-measuring foil in biomechanics]

Concerning the calibration of the Prescale foil - a pressure sensitive foil, which shows a monochromatic, pressure depending coloration when loaded - some interesting new facts were ascertained. The coloration of the foil does not depend on the pressure load only, but also on the material of the pressing bodies. Calibration using hard material (high Elastic-Module, e.g. steel) results in a lower maximal optical density compared to soft material (low Elastic-Module, e.g. a hydraulic system) at the same pressure level. Due to wellknown facts of the pressure conditioned in a joint, a hydraulic system is more equivalent to joint conditions. Therefore, a calibration method based on a hydraulic system should be preferred if the Prescale foil is used in biomechanics. Furthermore, the density of coloration depends on the speed of pressure increase, too. A faster load of a particular pressure results in a denser coloration. Pressure increase during calibration shall be the same as during investigation. Both effects are statistically significant.