DATA SIGNAL HANDLING IN COMPUTERIZED SYSTEMS

by Howard L. Skolnik ^[*]

Prior to the advent of the digital computer, industrial instrumentation and control systems, with comparatively few exceptions, involved analog, rather than digital, signals. This was true for both the outputs from sensors (input transducers strain gages, thermocouples, and so on) and the inputs to controlling devices (output transducers valves, motors, and so on). In modern systems many transducers are still inherently analog. This is important because computers can operate with only digital information. Therefore a majority of contemporary systems include analog-to-digital (A/D) and digital-to-analog (D/A) converters.

An important feature of data-acquisition products is how they bring together sophisticated functions in an integrated, easy-to-use system. Given the companion software that is available, the user can take advantage of the latest technology without being intimately familiar with the internal details of the hardware. When selecting a system, however, it is useful to have a basic understanding of data-acquisition principles. This article addresses how real-world signals are converted and otherwise conditioned so that they are compatible with modern digital computers, including personal computers (PCs). The techniques suggested here are specifically aimed at PC-based measurement and control applications. These generally involve data-acquisition boards that plug directly into an expansion slot within a PC. References to specific...