ASD series cell density probes from optek-Danulat provide users with the ability to measure and characterize cell growth to improve expression. Designed for bench-top, pilot and large-scale cell culture and fermentation, these autoclavable probes feature a one-piece stainless steel body and proprietary, seal-less sapphire optics. The ASD probes use a hybrid LED light source technology for maintenance-free operation. By measuring light in the near infrared region of the spectrum, ASD probes are able to measure optical densities greater than 800 OD in real-time.ASD probes display excellent accuracy and repeatability, even in fermentors with high aeration and agitation rates. Available in 19 mm and 25 mm sizes, the probes can be specified in a variety of insertion lengths and optical configurations to optimize measurement, resolution and performance for bacterial, mammalian, yeast and other cell cultures.