The Libra S2 is a small, robust, easy to use instrument that has been designed with both the student and field user in mind. It is ideal for teaching principles of science and analysis in schools and colleges, as well as being rugged enough for measurements in hot or demanding environments such as QC measurements in industrial processes or remote location health clinics where simple diagnostic tests need to be made. The samples can be measured in either standard or semi micro 10mm pathlength cuvettes or in 16mm diameter test tubes (adapters for 10/12 mm test tubes are available). The instrument surface is designed for ease of cleaning and decontamination. Rechargeable NiMH batteries are included in the Libra S2B and they will operate for almost a month on a single charge to provide complete portability. The instrument measures in Absorbance and % Transmission mode as well as in simple kinetics, enabling changes in Absorbance over time and reaction rates to be determined (readings are taken approx. every second). It may be used to cover the 400 – 700 nm wavelength range as it has an integral, colour coded rotating wheel containing filters at 440, 470, 490, 520, 550, 580, 590 and 680nm. These are made from coloured gelatin and are encased in glass, so that the instrument can be used in “tropical” conditions. A filter is selected by moving the wheel until the required wavelength is displayed in the window above the cell compartment.