Fault tolerant design of a field data modular readout architecture for railway applications

Modern data acquisition systems used to collect sensor signals are usually designed taking into consideration performance and operating parameters which are mainly related to sensitivity, selectivity, resolution and stability over time. In addition to such important features, field application systems should also respond to other constraints like reliability and availability and additionally, depending on the specific application, to some peculiar requirements in terms of safety. The present paper is addressed to supply an overview of the implications, during a sensor input/output hardware module design, of such parameters as the safety integrity level. The discussion involves the overall system design once integrated with availability considerations. In this manuscript, considerations concerning the on board software implementation are omitted without loss in generality. The study has been developed taking into account solutions suitable for railway applications like signaling or crossing detection systems.