Data Acquisition and Signal Processing for Smart Sensors

6

SIGNAL PROCESSING IN QUASI-DIGITAL SMART SENSORS

Digital signal-processing techniques are being used in a wide range of industrial and consumer products due to their accuracy and repeatability. According to Texas Instruments digital signal processing is defined as ‘The science concerned with representation of signals by sequences of numbers and the subsequent processing of these number sequences’ [131]. Processing involves either extracting certain parameters from a signal or transforming it into a form that is more applicable. The digital implementation of signal processing has several distinct advantages:

• It is possible to accomplish many tasks inexpensively that would be either difficult or impossible in the analog domain, for example, Fourier transforms.
• Digital systems are insensitive to environmental changes and component tolerances and ensure predictability and repeatability.
• Reprogrammability features.

Most signal-processing algorithms for quasi-digital smart sensors involve a multiply, divide and an add (subtract) operation which can be written in its general form as Equation (5.26). Before the appearance of embedded microcontrollers and DSP processors, these operations were realized in the quasi-digital domain with frequency–pulse signals. Because a smart sensor uses a microcontroller or a DSP microprocessor in its architecture, it is expedient to perform these operations in the digital domain. However, sometimes in time-critical applications as well as in automatic ...