Patent ID: 7965167

Claim:
A conductivity sensor for measuring conductivity of a medium surrounding the conductivity sensor, comprising: a multi-ply circuit board; a first toroidal coil bounding a medium-receiving passageway and serving for inducing an electrical current in the medium; and a second toroidal coil also bounding the passageway and serving for registering a magnetic field produced by the electrical current, wherein: at least one of the toroidal coils has a plurality of first conductor segments, which extend in a plane of said multi-ply circuit board, a plurality of second conductor segments, which extend in a second plane of said circuit board, and a plurality of through-contacts, which connect said first conductor segments with said second conductor segments; said first conductor segments, said second conductor segments and said through-contacts form, together, the windings of a toroidal coil; and when said first toroidal coil and said second toroidal coil are surrounded by the medium, said first toroidal coil can be operated as an exciter coil, inducing an electric current in the medium, the current being registered by said second toroidal coil.