The total cell density measurement is based on the optical density resp. the turbidity of a suspension at NIR wavelengths. All particles and molecules that scatter the NIR light will be detected and can be correlated to the total cell density. The Dencytee sensor keeps the light intensity at the detector constant leading to a wide linearity range. A measuring loop consists of a Dencytee sensor with an optical path length of 5 mm, a Dencytee pre-amplifier and the Arc View controller. The controller can display both parameters at once using the 2 (Arc View 265) or 4 (Arc View 465, 465 XL) channel inputs. Additionally Arc pH and DO sensors with a wireless module can be displayed on the controller giving the user the ability to regard all relevant parameters of a cell culture or fermentation on one screen. Denytee sensor and pre-amplifier are sold as Dencytee Unit but are also available as spare parts.