CHAPTER 2 - Data Acquisition and Coding

Abstract

This chapter discusses data acquisition and coding. In a single communication system, there may be many data sources each in a different form. Before the data items collected from all the sources can be correlated into useful information, all the items must first be transformed into a compatible form. The ultimate purpose of data acquisition is to bring all the source data-symbols into a uniform category, this being the binary form that is the common mould that would be used for computers. Data acquisition can be regarded as the front end of all communication systems. Source data could come in either analog or digital form. Analog form is derived from the outside world, while the digital form represents the data that is correlated with it. A third source of data may be used that represents a relatively steady state. Before one can exploit the data signals in one system, all the three data forms must be processed into a common binary form. Both the analog and state source data need similar numbers of processing stages, while the digital data requires little processing. The data contained in analog and state signals is generally full of redundancies, enabling the data to be scanned and even compressed. This is not the case in digital data, which contains no redundancies. The sensors used for each of the three data forms also require a different class of hardware devices. Analog data is received from transducers, digital data from keyboards, and state data from state readers.