Cell density meters are laboratory devices which determine the density of bacteria and yeast cells within a suspension. These spectrophotometers accomplish this by emitting a 500—700 nm wavelength and determining the absorbance (OD) of the cultures. A light source is filtered through a monochromator and an aperture. The light passes through the sample — a suspension held by a round tube or cuvette — where it encounters a photoresistor. Cell density meters are valued for their flexibility: they are commonly battery powered; they are easy to sterilize; and they can be used in anaerobic or incubator environments. Cell density meters interface with other equipment (computers, printers, etc.) via USB or serial lead.
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