This is an ultraviolet-visible light spectrophotometer, an instrument used to determine the concentration of a sample by measuring the absorbance of light travelling through it. Samples that can be used in devices like these range from compounds containing metals, to biological substances like proteins. The first spectrophotometer that could deliver accurate results in minutes - rather than weeks - was designed by Beckman Instruments in 1941. This company also designed the device displayed here, which dates from the 1960s.

This spectrophotometer is known as a DB-G grating spectrophotometer, which stands for ‘double beam grating’. These double beam versions are different from earlier spectrophotometers as they can compare the intensity of light passing through a reference sample with that passing through an experimental sample, whereas single beam devices can only analyse one sample at a time. This object represents one of the first types of the double beam machines, which were primarily designed to make measurements more stable and much easier to take than with the earlier single beam devices. Furthermore, this machine can be fitted with an attachment (not displayed here) that provides graphs of the absorbance results.

Modern spectrophotometers are very different to the apparatus displayed here, and double beam spectrophotometers can now be made small enough to be built onto specialised instruments such as microscopes. The range of spectrophotometers available today also includes some with the capacity to be connected to computers to generate output graphs more easily and with greater accuracy, while others are much more compact and simple - useful for teaching in undergraduate laboratories. Today’s spectrophotometers are generally much cheaper for similar functionality than this device from the 1960s. This piece of equipment cost NZ$2,595 at the time it was first released, which would be around $20,000 in today’s money, similar in price to some of the higher end spectrophotometers currently available.

Text by: Connor O’Rourke


Beckman Instruments Spectrophotometer, c.1960