Smart Sensor Systems

10

Universal Asynchronous Sensor Interfaces

Gerard C.M. Meijer and Xiujun Li

10.1 Introduction

Universal sensor interfaces form the ‘signal bridge’ between common sensing elements, which convert physical signals into electrical ones and the digital world. The functions of these interfaces include sensing, signal conditioning, analog-to-digital conversion, bus interfacing and data processing. Sometimes sensors and interface circuits can be implemented in single chips, called smart sensors. For instance, with acceleration sensors, it is quite possible to integrate the sensing element into micromachined chips, together with the required electronics for signal interfacing. Packaging such chips will not degrade the performance of these smart sensors. Also in the case of temperature sensors, it is quite possible to integrate electronic circuitry together with the sensing elements, provided that the self-heating caused by the power dissipation of the electronic circuitry does not cause inaccuracy (see Chapter 7). For other types of sensors there can be many reasons to implement the various parts of a sensor system separately, using different components. Usually, these reasons stem from physical or economical conditions and circumstances, such as:

• Harsh temperature conditions and corrosion disable the use of electronic circuits in an environment in which the sensing elements are operated.
• The product volumes are often far too low to make full integration economically feasible.
• Often, ...