Photoelectric colorimeter Lumetron Mod. 401. 1950.

Device for the measurement of the optical density of colored solutions, evaluated by a photocell. The test tube containing the sample is placed between a light source (filament lamp) and a selenium photocell. Between the lamp and the sample tube holder colored filters can be inserted to select the measuring wavelength. The photocell output varies depending on the amount of light received and is measured by a galvanometer, calibrated in percentage of transmitted light (T%) and in amount of light absorbed (Abs).