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Table 1 – Comparison of various hardware platforms for use in wireless sensor networks
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The last decade has seen an explosion in sensor technology. There are currently thousands of
potential sensors ready to be attached to a wireless sensing platform. Additionally, advances in
micro‐electromechanic devices (MEMS) and carbon Nano‐tubes technology are promising to create
a wide array of new sensors. They range from simple light and temperature monitoring sensors to
complex sensors able to monitor more parameters and work as ”digital noses” for electronic air
quality control etc.

2.3.2.4 Interfaces

There are two general ways to interface with sensors that can be used in sensor networks: analog
and digital. Analog sensors generally provide a raw analog voltage that corresponds to the physical
phenomena that they are measuring. Generally these produce a continual waveform that must be
digitized and then analyzed. While seemingly straightforward to integrate, raw analog sensors often
require external calibration and linearization. It is common for the sensor to have non‐linear
response to stimuli. The host controller must then compensate in order to produce a reading in
meaningful units. Depending on the characteristics of the sensor this can be a complex process. In
many cases the translation may depend on other external factors such as temperature, pressure, or
input voltage. A second difficulty in interfacing with raw analog sensors is that of scale. Each sensor
will have different timing and voltage scales. The output voltage will generally contain a DC offset
combined with a time‐varying signal. Depending on the ratio of signal to DC component, an array of
amplifiers and filters may be required to match the output of the sensor to the range and fidelity of
the ADC being used to capture it.
Digital sensors have been developed to remove many of these difficulties. They internally contain a
raw analog sensor, but provide a clean digital interface to it. All required compensation and
linearization is performed internally. The output is a digital reading on an appropriate scale. The
interface to these sensors is via one of a handful of standard chip‐to‐chip communication protocols.

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16 Extracted from http://www.isi.edu/~johnh/PAPERS/Conner04a.pdf

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