 I am Milka Jagle, working as assistant professor in Department of Mechanical Engineering, Walsham Institute of Technology, Solapor. Today, we are going to learn about sensors. At the end of this session, learners will be able to identify various types of sensors. So these are the contents for today's presentation. So these are the various types of sensors and we are going to see the various types of sensors which we found in our day-to-day life. So let us define what is a sensor. According to the Instrument Society of America, sensors can be defined as a device which provides a usable output in response to a specified measurement or it can also be defined as an element which subjected to some physical change experiences a relative change or when input is physical quantity and output is electrical then it can be called as a sensor. So here you can see the block where the physical parameter is converted into electrical output that is when the input is physical quantity and the output is electrical quantity then that can be called as a sensor. So what type of sensors we should use? There is a certain criteria on which the sensors can be selected. So the criteria are the accuracy, environmental condition, usually has a limits for temperature and humidity, the range that is measurement limit of a sensor and the calibration which is essential for most of the measuring devices as the readings change with time to time. So for every sensor calibration is one of the important aspect that should be taken into consideration. So now I want you to pause the video and just think about what are the different types of sensors you come across in your day-to-day life. For example, temperature sensor that is thermometer, flow sensor that is orifice meter or venturi meter or pitot tube. So list down the various sensors that you come across. Further we are going to discuss about what are the various sensors. So just list down those sensors. So first temperature sensor is a thermocouple. So as we see a thermocouple is made up of wires which form a measuring junction by one end. This measuring junction is open to the elements being measured and the other end of the wire is terminated to a measuring a reference junction is formed. The current flows through the circuit since the temperature of the two junctions are different. Figure one shows the thermocouple where there are two junctions that is cold junction and hot junction. The two wires that is wire of type A and wire of type B. The next temperature sensor is thermistor. They are another kind of thermal resistor where a large change in resistance is proportional to small change in temperature. Figure two shows the thermistor. The next type of sensor is a torque sensor. Torque sensor torque transducer or torque meter is a device for a measuring and recording the torque on a rotating system such as engine, crankshaft, gearbox, transmission, rotor, a bicycle crank or cap torque tester. The torque is relatively very easy to measure. A torque sensor or transducer converts torque into electrical signal. The strain gauge is bonded to a beam or structural member that deforms when a torque or force is applied. The deflection induces a stress that changes its resistance. A withstone bridge converts the resistance change into calibrated output signal. Figure number three shows the torque sensors which are used to measure the torques. The next type of sensor is a flow sensors. The flow rate sensor measures the velocity of water in studying the discharge, flow patterns and sediment transport of a stream or a river. The type of fluid flow meters are orifice, venturis, nozzles, rotameters, pitot tubes, calorometrics, turbine, vortex, electromagnetic, Doppler, ultrasonic and thermal. Figure number four and five shows the flow rate sensor and a rotameter which are used to measure the flow rate. The next type of sensor is infrared sensors. This device emits and detects infrared radiations to sense a particular phase in the environment. Generally, the thermal radiation is emitted by all objects in the infrared spectrum. The infrared sensor detects this type of radiation which is not visible to human eye. The advantages of infrared sensors are they are easy for interfacing and readily available in the market. The disadvantages are they get disturbed by the noses in the surrounding such as radiations and ambient lights etc. Figure number six shows infrared sensor. The next type of sensor we will see is ultraviolet sensor. The sensors measures the intensity or power of incident ultraviolet radiation. This form of electromagnetic radiation has wavelength longer than x-rays but is still shorter than visible radiation. An active material known as polycrystalline diamond is being used for reliable ultraviolet sensing. Ultraviolet sensors can discover the exposure of environment to ultraviolet radiation. Figure number seven shows ultraviolet sensor. Magnetic field sensor. Magnetic field sensors are used for power steering, security and current measurements on transmission lines. Figure number eight shows magnetic field sensor. Similarly the figure number nine also shows the magnetic field sensor. Ultrasonic sensors. The ultrasonic sensor is an instrument that measures the distance to an object using ultrasonic sound waves. An ultrasonic sensor uses a transducer to send and receive ultrasonic pulses that they rely back information about an object's proximity. Figure number six and seven shows ultrasonic sensors. The next type of sensor is a force sensor. Force sensors use load cells to weigh objects and prevent machinery from overloading. Force sensors are load cells transducers that convert force into measurable electrical outputs. The force sensors are majorly electronic equipments whose material can be force sensing register. Generally the working principle of force sensor is that they respond to the applied load and weigh and then transforms them into quantifiable output. Figure number eight shows load cell sensors whereas figure number nine shows force sensors. These are the applications of sensors in various fields that is shock detection, machine monitoring applications, vehicle dynamics, low power applications, structural dynamics, medical aerospace, nuclear instrumentation as pressure sensor in mobiles that is touch key pad, lamps which brighten or dim on touching its base and the finally that is touch sensitive buttons in the elevator. There are many applications which are using sensors but for time being we are we have jotted down just these applications. These are the references the book by Bolton, book by Shetty and Coke and book Mahalik by Tata McGraw-Hills. Thank you.