Cell Density monitoring comprises two technologies: viable cell density and total cell density. The viable cell density measurement is based on permittivity and gives the user a deep insight on their cell culture or fermentation. It’s insensitive to microcarriers and cell debris. The total cell density measurement is based on turbidity, resp. on optical density measurement at NIR (Near Infra-Red) wavelengths. The measuring loops for viable and total cell density monitoring consist of an Incyte resp. Dencytee sensor, an individual pre-amplifier and a Control Unit.