The Spectronic 20 is a spectrophotometer developed by Bausch & Lomb and launched in 1953. Approximately 600,000 units were sold over its nearly 60 year production run. Production was discontinued in 2011. Over 300,000 instruments are believed to remain in use in chemistry laboratories in both commercial and educational settings around the world.
The product line was sold to Milton Roy in 1985. Milton Roy sold its instrument group to Life Sciences International, renamed Spectronic instruments, Inc in 1995. Spectronics Instruments was purchased by Thermo Optekin 1997, renamed Spectronic-Unicam in 2001 and Thermo-Spectronic in 2002 in. In 2003 the product line was moved to Madison, WI and the brand renamed to Thermo Electron.
With the merger of Thermo Electron and Fisher Scientific in 2006 the brand changed to Thermo Scientific, and remained such until the end of the production run. Spectronic 20 instruments found in labs today may bear any of the Bausch and Lomb, Milton Roy, Spectronic, Thermo Electron or Thermo Scientific brands.
The original design utilized an analog dial for readout of transmission from 100%T to 1%T (top scale), 0A - 2A (lower scale). Using the original instrument requires manual setting of the wavelength and making readings from a moving-needle analog display. The Spectronic 20D (launched in 1985) and then 20D+ replaced the analog dial with a red LED readout, offering greater precision in the readout, if not greater accuracy in the actual reading. Spectronic 20 is rugged, accurate within the limits of is 20nm spectral bandwidth, and easy to use. The meter and educator versions were discontinued in December of 2010 and the 20D+ was discontinued at the end of 2011.
The Spectronic 20 was replaced by the Spectronic 200 in the Thermo Scientific spectrophotometer product line. The new model utilizes an array detector and digital control of the measured wavelength, while retaining the characteristic λ knob of the SPEC 20 for setting the wavelength. In addition to replicating the user modes of the Spec 20D+ (which it can emulate on a color LCD screen) the Spec 200 accommodates both test-tubes and square cuvettes without needing to install an adapter. Software modes in the new instrument include scanning, four wavelength simultaneous measurement and quantitative analysis with up to four standards, in contrast to the SPEC 20D+ which offered only single point calibration.