B. Sensor Nodes
Sensor devices are mounted on boards. The boards form
a platform combining mobile computing and wireless communication
(media access control (MAC), routing and error
detection) with sensor devices as shown in Fig. 2. Many sensor
nodes are moving toward enabling data interrogation and
autonomous data processing to identify anomalies in situ.
Hence, many data processing algorithms have also been embedded
in wireless sensor nodes for autonomous execution [80].
The boards generally comprise one or more wireless sensors,
a microcontroller, transceiver, data storage (memory), and a
power source. If the data sampling rate is low, for example,
when monitoring the growth of a crack over a period of time,
then the microcontroller, memory, and transceiver power can
all be low. However, for frequent sampling such as monitoring
the temperature of a mechanical bearing every second, then
the microcontroller, memory, and transceiver must be more
powerful. Lynch and Loh [80] provided a thorough overview
of sensor boards for WSNs.