The New CHROMA Range of Programmable Colorimeters

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Sherwood Scientific manufactures a range of four CHROMA clinical colorimeters: the Model 252 Analogue, and three new user programmable photometers:

• Model 260 Basic
• Model 264 Programmable Photometer
• Model 267 Clinical Analyser with 340 nm capability.

This new range, together with an extensive array of accessories provides a comprehensive solution to your colorimetric analysis requirements.

The basic design of the Sherwood CHROMA series of colorimeters has been stable for several years and has an enviable world-wide reputation for its rugged performance across the range. For the 21st century Sherwood Scientific has updated its photometer range and added a sophisticated software package unique in this class of instrument. The range offers features not elsewhere available and provides solutions to the requirements of quality control, water testing and especially for the clinical chemist for low sample runs. All four units have a long pedigree dating from the Model 2, the first commercial colorimeter in the UK, developed by EEL in 1950. The original model 252 colorimeter became the most widely used colorimeter in the world.

All units can be battery powered and thus can be used outside the Laboratory.

All of the accessories except the Printer will fit all three units, leaving the analyst to decide which is most appropriate to the task in hand.

The CHROMA Model 252 Analogue Colorimeter

The market leading analogue colorimeter. Featuring a mirror parallax- reducing combined Optical Density and % Transmission scale. This is used in education to establish the relationship between OD and %T. The Model 252 also is recommended in QC protocols which measure absolute OD compared with a control solution. Apart from a face lift we have not changed this winner.

The CHROMA Model 260 Programmable Colorimeter

This Model replaces the CHROMA 257 optical specification and now incorporates full programmability allowing up to 100 methods to be installed by the user. This permits semi-automatic operation with the user only required to insert the prompted filter. An RS232 output allows the use of a serial printer and every result, blank and calibration is time stamped. The unit allows quick Absorbance and Transmission measurements with Auto-Zero, Concentration with Standard Solutions or Factor as well as the new Kinetic Reaction Rate and End Point methods.

The CHROMA Model 264 Automatic Programmable Colorimetry

This Model represents a major technological improvement on the Model 257. We now have incorporated a filter wheel containing 8 filters with wavelengths from 405 to 600 nm. (See separate description) This model also benefits from all the programmability in common with the Model 260. In addition, when using the programmed methods, the Model 264 automatically introduces the filter of wavelength appropirate to the method chosen. These methods can cover water testing, clinical chemistry tests and many other methods chosen by the user.

The CHROMA Model 267 "The Clinical Chemists Choice"

The top-of-the-range Model 267 incorporates a near UV capability, Filter wheel and 20 preloaded diagnostic protocols. These protocols cover the more common tests . The CHROMA range is a fully open system so these protocols can be edited by the user to comply with the laboratories preferred methods. Up to 100 methods can be programmed by the user. The Model 267 also includes a 340 nm Interference filter which is inserted into a separate filter holder.

Temperature and the new CHROMA range

The new CHROMA range has two options to control the temperature of reactions. The low cost option is to use external temperature control by means of solid block heating. The software built in to all three of the new models includes the setting of Incubation (or lag time) and Measuring time. Towards the end of these times the user is alerted to return the cuvettes containing the blank sample or calibrant to the colorimeter by means of a buzzer. The relevant reading is taken and the cuvette is returned to the heating block to complete the rest of the test.

Sherwood has also developed an electrically heated cuvette holder designed specifically for the micro cuvettes used in the Model 267. This is able to control the temperature to 37 °C ± 0.1°C. and is available as an option.

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