Acquisition and processing of measurement signals using microprocessors - Global architecture: sensors and measurement chains

The acquisition, over time, of data relating to the state of a physical system enables it to be observed: the aim is to provide information on the temporal evolution of various physical quantities. The latter are judiciously chosen according to the desired aim: to enable the study of a scientific phenomenon, to generate optimal process control, to monitor the wear and tear of a production tool or, more simply, to guarantee the smooth running of an industrial system. Whether in research laboratories or on industrial production sites, the acquisition and processing of measurement signals are essential.

Furthermore, with the development of microprocessor-based systems, the computer and its computing capabilities were democratized to the point where they could be embedded within measurement and control systems. From this point onwards, the predictable evolution was to increase the share of digital technology to reduce the number of circuits required, thus cutting manufacturing costs and increasing reliability. This explains why microprocessors play such an important role in the design of electronic instrumentation systems. The use of a standardized sequential machine – the – microprocessor thus makes it possible to substitute the development of calculation software for the design and production of an entire analog and digital signal processing and conditioning chain. The advantages in terms of cost and flexibility are obvious. And "digital signal processing" was one of the first things to take off.

Finally, the ever-increasing integration density achieved in the manufacture of electronic circuits means that an ever-greater proportion of the sequential part can be replaced by hardwired logic, implemented using programmable logic circuits. This helps to reduce calculation times and thus increase the performance of data acquisition and processing systems, without any loss in design and maintenance flexibility: it is no longer rare to find the microprocessor associated with an FPGA, or even an FPGA alone integrating, among other things, the microprocessor!

This article reviews the architecture of a microprocessor-based data acquisition and processing chain, distinguishing its fundamental components and illustrating their specific roles with selected examples. This comprehensive overview is divided into two sections: the first [R 525v2] is devoted to sensors and associated measurement chains, while the second [R 526v2]...