A method of identifying, by a data logger unit, a sensor unit for an absorbent article, the sensor unit comprising a sensor-side terminal portion and at least one sense element (111, 112, 113, 114) electrically connected to at least one measurement terminal of the sensor-side terminal portion, the data logger unit comprising a logger-side terminal portion and a measurement module electrically connected to at least one measurement terminal of the logger-side terminal portion, the sensor-side terminal portion engaging the logger-side terminal portion so as to bring terminals of the sensor-side terminal portion into electrical connection with corresponding terminals of the logger-side sensor portion, the data logger unit adapted to perform an electrical measurement of the at least one sense element via the at least one measurement terminal of the sensor-side terminal portion and the at least one measurement terminal of the logger-side terminal portion, the data logger unit having a plurality of identification terminals at the logger-side terminal portion electrically connected to the measurement module; the sensor-side terminal portion having a plurality of identification terminals at the sensor-side terminal portion; the measurement module performing an electrical measurement of the plurality of identification terminals of the logger-side terminal portion, to identify a characteristic property of the sensor unit, the characteristic property of the sensor unit being encoded in the electrical potentials of the identification terminals of the sensor-side terminal portion, the method being characterised by the sensor-side terminal portion having a reference terminal; the logger-side terminal portion having a reference terminal; the measurement module providing a reference potential to the reference terminal of the logger-side terminal portion; at least one of the identification terminals of the sensor-side terminal portion being electrically connected via a conductor of the sensor unit to the reference terminal of the sensor-side terminal portion; the characteristic property of the sensor unit being encoded in the potentials at each of the identification terminals of the sensor-side terminal portion as compared with the reference potential. the sensor unit comprising a sensor-side terminal portion and at least one sense element (111, 112, 113, 114) electrically connected to at least one measurement terminal of the sensor-side terminal portion, the data logger unit comprising a logger-side terminal portion and a measurement module electrically connected to at least one measurement terminal of the logger-side terminal portion, the sensor-side terminal portion engaging the logger-side terminal portion so as to bring terminals of the sensor-side terminal portion into electrical connection with corresponding terminals of the logger-side sensor portion, the data logger unit adapted to perform an electrical measurement of the at least one sense element via the at least one measurement terminal of the sensor-side terminal portion and the at least one measurement terminal of the logger-side terminal portion, the data logger unit having a plurality of identification terminals at the logger-side terminal portion electrically connected to the measurement module; the sensor-side terminal portion having a plurality of identification terminals at the sensor-side terminal portion; the measurement module performing an electrical measurement of the plurality of identification terminals of the logger-side terminal portion, to identify a characteristic property of the sensor unit, the characteristic property of the sensor unit being encoded in the electrical potentials of the identification terminals of the sensor-side terminal portion, the method being characterised by the sensor-side terminal portion having a reference terminal; the logger-side terminal portion having a reference terminal; the measurement module providing a reference potential to the reference terminal of the logger-side terminal portion; at least one of the identification terminals of the sensor-side terminal portion being electrically connected via a conductor of the sensor unit to the reference terminal of the sensor-side terminal portion; the characteristic property of the sensor unit being encoded in the potentials at each of the identification terminals of the sensor-side terminal portion as compared with the reference potential.