Contact resistance between interlaced conductive yarns will under certain circumstances constitute a problem for sensor applications and electrical routing in interactive textile structures. This type of resistance could alter the effective area of the sensor and introduce hot-spots in the routing. This paper presents a technique for measuring contact resistances on fabric samples. The samples used are unit cells of plain weave, that is, two conductive (silver-coated) yarns in the warp direction and two in the weft direction. The numerical values for the contact resistance are of the order of Rc ≈ 0.3 Ω. A resistor network made of through-hole film resistors with known values is used for evaluation of the method. The results show that the technique provides values typically within ±1% error compared with the known resistor values. Thus, the method can be used in order to calculate the contact resistances of a woven conductive textile.

The rise of interest in wearable sensing of bioelectrical signals conducted via smart textile systems over the past decades has resulted in many investigations on how to develop and evaluate such systems. All measurements of bioelectrical signals are done by way of electrodes. The most critical parameter for an electrode is the skin-electrode impedance. A common method for measuring skin-electrode impedance is the two-lead method, but it has limitations because it relies on assumptions of symmetries of the body impedance in different parts of the body as well as of the skin-electrode impedances. To address this, in this paper we present an easy-to-use and reliable three-lead in vivo method as a more accurate alternative. We aim to show that the in vivo three-lead method overcomes all such limitations. We aim at raising the awareness regarding the possibility to characterize textile electrodes using a correct, accurate and robust method rather than limited and sometimes inadequate and uninformative methods. The three-lead in vivo method eliminates the effect of body impedance as well as all other contact impedances during measurements. The method is direct and measures only the skin-electrode impedance. This method is suitable for characterization of skin-electrode interface of textile electrodes intended for both bioelectrical signals as well as for electrostimulation of the human body. We foresee that the utilization of the three-lead in vivo method has the potential to impact the further development of wearable sensing by enabling more accurate and reliable measurement of bioelectrical signals.