An impedance matching element is disclosed which can be used for voltage and/or current sensing or indicating devices used in medium voltage systems in order to improve signal integrity of output signals in comparison with known sensing devices. To enhance sensing accuracy and provide higher output signal immunity against interferences and impedance mismatches, the electric field sensor and/or the magnetic field sensor can be connected to the impedance matching element which allows connection to an independent analog measuring device and is powered from an energy harvester, with an impedance matching electronic board.