Abstract: This invention relates to a sensor assembly and a method for measuring characteristics of a surface, preferably skin, comprising a first pair of current supply electrodes coupled to a current source, providing an electrical current to the skin, at least one pickup electrodes at chosen positions relative to the current supply electrodes, at least a first of said pickup electrodes being coupled to an instrument for measuring the voltage between said first pickup electrode and at least one of the pickup or current supply electrodes.

Abstract: Method and sensor assembly determining the condition of a structure, especially for confirming if a measured fingerprint is on a live finger, by measuring characteristics of close to the structure surface, the sensor comprising a first pair of current supply electrodes coupled to a current source, providing an electrical current to the skin, at least two pickup electrodes at chosen and different positions relative to the current supply electrodes, at least a first of said pickup electrodes being coupled to an instrument for measuring the voltage between said first pickup electrode and at least one of the pickup or current supply electrodes, storage means for a predetermined set of values characterizing a certain condition of the surface, and means for comparing the characteristics from each pickup electrode with the measurements of the other pickup electrodes and with the predetermined set of characteristics for determining the surface condition.

Abstract: Sensor device for performing measurements on an at least partially conductive surface, the sensor comprising a number of conductive structures at or directly below the sensor surface, said conductive structures consisting of at least one stimulation or current sink electrode 1 and a number of sensor elements 3 coupled to interrogation electrodes in an electronic circuit for measuring impedance between the electrodes 3 and said at least one stimulus electrode 1, the sensor device also comprising at least one additional clamping electrode being positioned in the vicinity of said sensor elements and being coupled to a chosen voltage.