【正文】 peripherals and interfaces. System design is based around 80C31 microcontroller [4] connected through address bus, data bus, and control bus to the 64 kbytes of EPROM 27C512 for monitor and control program, 24 kbytes of RAM with battery backup for temporary data storage, 24hour results storage capacity, and peripheral I/O devices 8255 s are used for interfacing 32key keyboard, 12bit A/D converter, 40 column thermal mini printer, and 30 characters 8 lines alphanumeric/graphic LCD display. Alphanumeric keyboard contains various function keys, numeric keys and aspirate and RESET key for selecting various functions of the system and parameter LCD is used for displaying date and time by realtime clock, various menus, parameters and data entered from keyboard as well as patient’s results and kiic graphs as required in some test parameters. 12bit A/D converter converts analog signal from photo detector and preamplifier into digital form. 40 column thermal mini printer is used for hard copy of the parameters stored, patient test results, collection report, and kiic graphs as displayed on the LCD. These graphs facilitate authenticity of the test results. (iii) Peltierbased temperature controller System developed is used to determine both enzyme activity and substrate concentration in biological fluids at different temperatures 25 176。 Management in Chemistry, India Clinical chemistry analyser is a highperformance microcontrollerbased photometric biochemical analyser to measure various blood biochemical parameters such as blood glucose, urea, protein, bilirubin, and so forth, and also to measure and observe enzyme growth occurred while performing the other biochemical tests such as ALT (alkaline amino transferase), amylase, AST (aspartate amino transferase), and so forth. These tests are of great significance in biochemistry and used for diagnostic purposes and classifying various disorders and diseases such as diabetes, liver malfunctioning, renal diseases, and so forth. An inexpensive clinical chemistry analyser developed by the authors is described in this paper. This is an open system in which any reagent kit available in the market can be used. The system is based on the principle of absorbance transmittance photometry. System design is based around 80C31 microcontroller with RAM, EPROM, and peripheral interface devices. The developed system incorporates light source, an optical module, interference filters of various wave lengths, peltier device for maintaining required temperature of the mixture in flow cell, peristaltic pump for sample aspiration, graphic LCD display for displaying blood parameters, patients test results and kiic test graph, 40 columns mini thermal printer, and also 32key keyboard for executing various functions. The lab tests conducted on the instrument include versatility of the analyzer, flexibility of the software, and treatment of sample. The prototype was tested and evaluated over 1000 blood samples successfully for seventeen blood parameters. Evaluation was carried out at Government Medical College and Hospital, the Department of Biochemistry. The test results were found to be parable with other standard instruments. 1. INTRODUCTION In order to measure the progress of an enzymatic reaction and to measure the total change in the concentration of the reactant/substrate, various techniques [1] such as spectrophotometric, polarometric, amperometric, electrochemical, coulometric, polarography, radiochemical, and fluorescence are available. Instrument developed works on the principle of absorbance transmittance photometry. It is a highperformance,microcontrollerbased, photometric biochemical analyser to measure various blood biochemical parameters such as blood glucose, urea, protein, bilirubin, and so forth, and also to measure and observe enzyme growth occurred while performing the other biochemical tests such as ALT (alkaline amino transferase), amylase, AST (aspartate amino transferase), and so forth. The biochemical tests are very important as they are associated with various disorders and diseases such as diabetes, renal diseases, liver malfunctions,and other metabolic derangements. The quantisation of these parameters helphful in classifying such diseases,and under appropriate circumstances, results are used for diagnostic recent years, automation in clinical chemistry has progressed with a change from rigid to very flexible instruments. Automation of clinical instruments has brought about a revolution in the field of medical instrumentation. It has reduced 12 the load on clinical laboratories to a great extent by reducing the time taken in the test and minimizing the involvement of laboratory staff. Instrument developed is classified as semiautomated analyser [2] and has advantages of precision and accur