A Data Acquisition System (DAS) is the term given to one or more units that are used to collect and condition data from one or more sources. A modular DAS is one that consists of a ‘chassis’ which contains a number of ‘modules’. The modular construction allows for custom systems to be built using off the shelf modules. There are typically two types of modular systems – semi-modular systems and fully modular systems.
Semi-modular systems typically allow a user to customized some elements of the DAS, but the system may be locked in terms of interconnection technologies and incompatible with different generations of chassis and ranges of modules limiting reuse and the ability to exploit existing resources. Truly modular systems use modular controllers and stable chassis design; thus the entire modular data acquisition system is fully customizable and product can remain compatible over decades. Semi-modular systems can be used with different DAS as long as they appear as compatible systems as far as programing, management and data transmission software and protocols are concerned. Ethernet in particular holds promise as being a catch-all technology that can connect hardware from different families of products or even different vendors. Initiatives such as iNET/iNET-X and XidML are attempting to achieve this kind of inter-hardware compatability.