TABLE OF CONTENTS Elena Gaura
Robert Newman
The sensor read-out circuit (sometimes called sensor interface or sensor pick-off) enables a MEMS sensing element to become a fully functional MEMS sensor or transducer. Whilst two decades ago describing the readout/interfacing techniques for sensors would have been a relatively straightforward matter, this is no longer the case, as interface circuits of today are no longer just an essential block of electronics to be placed behind the sensing device in order for the sensing task to be accomplished. As new generations of cheap and smart sensors (meaning easy-to-use for most people) are being developed and finding their way into applications, the interface circuits have evolved to encompass signal conditioning circuits, ADCs, bus interfaces and sometimes data (or even information) communication circuitry and sensor networking facilities. This, added to the sensor specific design techniques being developed for increased accuracy, low power consumption and the speculative integrated decision making capabilities foreseen for deployed sensors, makes the task of this chapter a rather difficult one.
Separating the sensor interface electronics from the sensor electronics in terms of current designs and implementations on one hand and tracing the particulars of various interface function implementations (filtering, signal separation, signal conversion) in sensing applications lead designs, on the other hand, is almost impossible. Consequently, the approach to discussing the sensor electronics , in this chapter, is by pointing out the interface requirements and characteristics of MEMS sensors in the context of the sensor as a digital or mixed signal processing system.
