The viable cell density measurement is based on permittivity. Viable cells behave like little capacitors and their polarization and depolarization in an alternating electrical field is measured. The signal can be correlated to the bio-volume, resp. the viable cell density. Only viable cells can be polarized, so this meathod is insensitive to cell debris as well as to microcarriers. A measuring loop consists of an Incyte sensor that is available in different dimensions, an Incyte pre-amplifier and an Arc View controller.