This PPT presentation is based on the topic SENSOR TECHNOLOGY
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WHAT IS SENSOR?
►A device that measures or detects a real world condition, such as motion, heat or light and converts the condition into an analog or digital representation.
► A device that measures a physical quantity and converts it into a signal which can be read by an observer or by an instrument.
A mercury in glass thermometer converts the measured temperature into expansion and contraction of a liquid which can be read on a calibrated glass tube.
A thermocouple converts temperature to an output voltage which can be read by a voltmeter.
For accuracy, all sensors need to be calibrated against a known standards.
A good sensor obeys the following rules:
• Is sensitive to the measured property
• Is insensitive to any other property
• Does not influence the measured property
Ideal sensors are designed to be linear. The output signal of such a sensor is linearly proportional to the value of the measured property. The sensitivity is then defined as the ratio between output signal and measured property. For example, if a sensor measures temperature and has a voltage output, the sensitivity is a constant with the unit [V/K]; this sensor is linear because the ratio is constant at all points of measurement.
If the sensor is not ideal, several types of deviations can be observed:
The sensitivity may in practice differ from the value specified. This is called a sensitivity error, but the sensor is still linear.
Since the range of the output signal is always limited, the output signal will eventually reach a minimum or maximum when the measured property exceeds the limits. The full scale range defines the maximum and minimum values of the measured property.
The resolution of a sensor is the smallest change it can detect in the quantity that it is measuring. Often in a digital display, the least significant digit will fluctuate, indicating that changes of that magnitude are only just resolved. The resolution is related to the precision with which the measurement is made. For example, a scanning tunneling probe (a fine tip near a surface collects an electron tunneling current) can resolve atoms and molecules.
TYPES OF SENSOR
All living organisms contain biological sensors with functions similar to those of the mechanical devices described. Most of these are specialized cells that are sensitive to:
Light, motion, temperature, magnetic fields, gravity, humidity, vibration, pressure, electrical fields, sound, and other physical aspects of the external environment
Physical aspects of the internal environment, such as stretch, motion of the organism, and position of appendages (proprioception)
Environmental molecules, including toxins, nutrients, and pheromones
Estimation of biomolecules interaction and some kinetics parameters
Internal metabolic milieu, such as glucose level, oxygen level, or osmolality
Internal signal molecules, such as hormones, neurotransmitters, and cytokines
Differences between proteins of the organism itself and of the environment or alien creatures
WORK FUNCTION & USES
WHEN SENSOR RECEAVES THE DATA, THEN IT TRANSFER TO THE ACTUATOR AND THEN TO THE MICROCONTROLER AND MICROCONTROLER TRANSFER IT INTO THE DC MOTOR AND DC MOTOR FUNCTION THE WORK.
Sensors are used in everyday objects such as touch-sensitive elevator buttons (tactile sensor) and lamps which dim or brighten by touching the base. There are also innumerable applications for sensors of which most people are never aware. Applications include cars, machines, aerospace, medicine, manufacturing and robotics.
USED IN WIRELESS NETWORK
Wireless communication is the transfer of information over a distance without the use of enhanced electrical conductors or "wires". The distances involved may be short (a few meters as in television remote control) or long (thousands or millions of kilometers for radio communications). When the context is clear, the term is often shortened to "wireless". Wireless communication is generally considered to be a branch of telecommunications.
It encompasses various types of fixed, mobile, and portable two-way radios, cellular telephones, personal digital assistants (PDAs), and wireless networking. Other examples of wireless technology include GPS units, garage door openers and or garage doors, wireless computer mice, keyboards and headsets, satellite television and cordless telephones.
Wireless sensor network
Typical Multihop Wireless Sensor Network Architecture
A wireless sensor network (WSN) consists of spatially distributed autonomous sensors to cooperatively monitor physical or environmental conditions, such as temperature, sound, vibration, pressure, motion or pollutants. The development of wireless sensor networks was motivated by military applications such as battlefield surveillance. They are now used in many industrial and civilian application areas, including industrial process monitoring and control, machine health monitoring, environment and habitat monitoring, healthcare applications, home automation, and traffic control.
In addition to one or more sensors, each node in a sensor network is typically equipped with a radio transceiver or other wireless communications device, a small microcontroller, and an energy source, usually a battery. A sensor node might vary in size from that of a shoebox down to the size of a grain of dust, although functioning "motes" of genuine microscopic dimensions have yet to be created. The cost of sensor nodes is similarly variable, ranging from hundreds of dollars to a few pennies, depending on the size of the sensor network and the complexity required of individual sensor nodes. Size and cost constraints on sensor nodes result in corresponding constraints on resources such as energy, memory, computational speed and bandwidth.
A sensor network normally constitutes a wireless ad-hoc network, meaning that each sensor supports a multi-hop routing algorithm (several nodes may forward data packets to the base station).
In computer science and telecommunications, wireless sensor networks are an active research area with numerous workshops and conferences arranged each year.
The applications for WSNs are varied, typically involving some kind of monitoring, tracking, or controlling. Specific applications include habitat monitoring, object tracking, nuclear reactor control, fire detection, and traffic monitoring. In a typical application, a WSN is scattered in a region where it is meant to collect data through its sensor nodes.