A sensor is a physical device or biological organ that detects, or senses, a signal or physical condition and chemical compounds. There are various types of sensors used for different purpose. Among them, Passive sensors and active sensors are the most basic types of sensor. Passive sensors are used for detecting the reflected or emitted Electro-magnetic radiation from natural sources, while active sensors are used to detect reflected responses from objects which are irradiated from artificially generated energy sources, such as radar.
Further, each type of sensor is divided into two classes namely non-scanning and scanning systems. A sensor having a combination of passive, non-scanning and non-imaging method belongs to class of profile recorder, for example a microwave radiometer. A sensor having a combination of passive, non-scanning and imaging method belongs to class of camera-type devices, for example an aerial survey camera or a space camera.
Sensors classified as a combination of passive, scanning and imaging are further classified into two category viz. image plane scanning sensors, such as TV cameras and solid state scanners and object plane scanning sensors, such as multi-spectral scanners (optical-mechanical scanner) and scanning microwave radiometers.
In addition to this kind of classification, sensors can be classified according to the type of energy transfer that they detect. The various types of sensors are Thermal energy sensors, Electromagnetic sensor, Mechanical sensors, Chemical sensors, Optical and Radiation sensors, Ionizing radiation sensor, non-Ionizing radiation sensors, acoustic sensors and biological sensors.
Sensors can be used to monitor conditions at different locations, such as temperature, sound, vibration, pressure, motion or pollutants. Sensors used for such purpose are usually small and inexpensive, so that they can be produced and deployed in large numbers. In addition, it also helps to decrease resources in terms of energy and increases memory, computational speed and bandwidth.
In such network, numbers of sensors are deployed across a geographical area. Each sensor has wireless communication capability and some level of intelligence for signal processing and networking of the data. To be precise, each device consists of a radio transceiver, a small microcontroller, and an energy source (battery). These devices communicate with each other to deliver data to a monitoring computer. The areas covered by Sensor network are sensing, communications, and computation (hardware, software, and algorithms). After this process, data from the sensors is collected and analysed by a computer outside the network. This computer is connected to the network by a special network node called a gateway node or sink or base station
Sensor networks are implemented in various areas for different purposes, like video surveillance, traffic monitoring, air traffic control, robotics, cars, home and health monitoring and manufacturing and industrial automation. One typical application in environmental monitoring is Sensor Web.
Besides this, it is also used by military service to detect and gain as much information as possible about enemy movements, explosions, and other phenomena of interest.
Sensor has evolved as a great player in industrial application and in other areas also due to its ability to operate at much higher speeds; conduct repetitive, multiple, and consistent inspections all at significantly lower cost.
Furthermore, it has the potential to change the working of industrial world, making working process quicker and simpler. But, the challenge doesn`t end here. In the upcoming days, the biggest challenge for the engineers will be to manufacture a sensor, which is capable of tolerating any bad conditions, such as weather, chemicals, dust and humidity against electromagnetic interference (EMC).