STEP-BY-STEP DEVELOPMENT OF AN ELECTROCHEMICAL MICROANALYTICAL SYSTEM

The development of an electrochemical microanalytical system for ionom etric measurements (acronym ELMAS) is described. ELMAS combines potent iometric microsensors with solid state ion sensitive membranes, plasti c molded and adhesive mounted micropumps, a microchannel system for co nnecting all components (several sensors, the calibrating solution res ervoirs, the micropumps) and microelectronic components for signal pro cessing and system control. The development of any complex technical s ystem requires a good understanding and asks for a specification of hi gh quality. Very useful for this purpose are executable specifications ; they can demonstrate system properties already in an early design st age and give a deep insight in the behaviour of the system. Thus the s ystem requirements can be verified and design errors can be detected a nd eliminated earlier than by other approaches. So we started the deve lopment of the ELMAS microsystem with the creation of a dynamical exec utable specification model, based on Statecharts, performed by the STA TEMATE tool. Statecharts are extended finite automata. This model has been combined with a graphical user interface. Running simulations gua rantees the correct system behaviour. The graphical interface itself w as used for communication between the institutes participating on the development of ELMAS. The next stage of development was characterized by substituting some simulated components by real ones. At this stage microsensors have been combined with macro pumps and conventional elec tronics. The model running on a workstation controls the sensor and ac tuator components of macro dimension. The result of this stage was a m acro prototype of ELMAS. It was used for testing the new developed mic rosensors and analysing the system behaviour. Going from the macro to micro components and replacing the workstation by a microcontroller th e step by step development of ELMAS ends up in a real microsystem for the simultaneous measurement of pNa and pH. Thus we get a closed chain from specification to realization.