Sensors

Sensing is a technique which is used to gather information about any object or events or process.

An object which is performing a sensing process is called as Sensors. Another term which is commonly used is Transducer. A transducer is an electronic device that converts the energy from one form to another.

An actuator is a device that converts energy into motion. Hence it is an explicit type of transducer. When the output of the transducer is converted to a readable format, the transducer is called a sensor. A sensor is a device that receives and responds to a signal. A sensor can detect and responds to some type of input from the physical environment. The specific input could be light, heat, motion, moisture, pressure or any one of a great number of other environmental facts.

A Wireless Sensor Network (WSN) can be defined as a network of devices that can communicate the information gathered from a monitored area through a wireless link. WSN is a wireless network that consists of base stations and a number of nodes. These networks supervise physical or environmental conditions like sound, pressure, temperature and then pass the data through the network to the main area.

A sensor node is also called a Mote which is able to perform some processing, gathering data and communicating with further connected nodes in the network. The sensor nodes collect the data from the surroundings and send to the base station. From the base station, it reaches to the user. The communication between the nodes can be done with each other using transceivers. In a wireless sensor network, there can be a number of motes which can be in the order of hundreds or even thousands.

The characteristics of WSN include the following:

• Minimum Power Consumption

As sensor nodes are very small in size, they can store or produce only a limited amount of energy from the environment.

• A chance to handle node failures (Resilience)

Due to environmental factors, nodes can be subject to failures. Limited size and energy also restrict resources such as CPU performance, memory, communications and coverage range.

• Limited Communication

The transmission range is mainly depended on the geographical environment and the natural cause. It varies from tens of meters to hundreds of meters. The bandwidths of the sensor nodes are limited.

• Heterogeneity of nodes

Different types of nodes with different transmission radii can be deployed in the area.

• Mobility of nodes

It is not easy to put into action a large scale as well as a mobile wireless sensor network. By the mobility of nodes, the sensor moves into positions that help to minimize the energy cost.

• Unattended operation

The operations are performed automatically by the sensor, allowing the handling of signals or data without intervention.