Abstract: A device for monitoring the electrical conductivity of an electrically conductive fluid comprising at least two electrical coils for immersion in the fluid. One of the coils constitutes a coil to be energized with an alternating current and the other in use constitutes a detection coil. The coils are arranged relative to one another so that in use they are mutually inductively coupled and are inductively coupled by the fluid.An electronic circuit is provided which includes a power supply for supplying an alternating current to the coil or coils to be energized, and a detector for detecting the voltage induced in the detection coil or coils. The detector provides an indication of changes in the inductive coupling between the coil or coils to be energized and the detection coil or coils.