The first prototype Beckman spectrophotometer, the Model A, was created at National Technologies Laboratories in 1940. It used a tungsten light source with a glass Fery prism as a monochromator. Tungsten was used for incandescent light filaments because it was strong, withstood heat, and emitted a steady light. Types of light sources differed in the range of wavelengths of light that they emitted. Tungsten lamps were useful in the visible light range but gave poor coverage in the ultraviolet range. However, they had the advantage of being readily available because they were used as automobile headlamps. An external amplifier from the Beckman pH meter and a vacuum tube photocell were used to detect wavelengths.
