Abstract: An apparatus and method continuously samples and measures the changing concentration and/or density of suspended solids in a liquid medium without electrical connections at the submerged points in the liquid. A submersible sensing head is connected by an elongate probe to an non-submersible enclosure which contains at least one light source and one light detector. The sensing head has an apertured sample chamber allowing liquid to flow freely therethrough when submerged and contains at least one light emitting lens and at least one light receiving lens aligned in the flow path. The light emitting lens is connected to the light source and the light receiving lens is connected to the light detector with fiber optic bundles extending the probe. An elongate shaft extends through the probe and into the sensing head sample chamber and has a lens wiper at its lower end.