 Welcome to the session. Today's topic of the discussion is the reluctance and photoelectric pickup sensors. My name is Ajit Subhash Suryanshu, working as an assistant professor in the electronic telecommunication department at the Walsh Institute of Technology. So today's topic of the discussion is at the end of the session, students will be able to select the appropriate transducer to measure the physical parameters like the count, the speed and the displacement. So what is a prerequisite? That is what should knowledge you possess before proceeding to this session is that you should have a knowledge of the different materials, which is especially the electrical properties. And you should have a knowledge of the basic circuit analysis, that is electrical circuit analysis. So let's start with the reluctance pickup. So reluctance name itself suggests a reluctance in the magnetic path. So reluctance pickup, it is also called as a VR sensor or variable reluctance sensors. It is a type of the transducer which converts the changing reluctance into the equivalent current because current and the reluctance are directly proportional. So when there is a change in the reluctance of the coil or in the magnetic field, the current associated with also changes. So if you see there is a gear is here and these are the tools are there. When this gear shaft is rotating, so when there is a rotation, the magnetic reluctance of this coil changes because the permeability change is happening there. So when there is a teeth is at the vicinity of this permanent magnet coil. So in that case, it have a lower reluctance and when there is a no teeth, that is it has a higher reluctance. So in the case of there is a teeth, you will get the larger amount of the current and in the case of absence of the teeth, you will get the smaller amount of the current. So in short, you will get the one pulse for the one teeth. So at this transformer action, this is the primary side of the transformer. This is secondary side of the transformer. So you will get the pulse for the every teeth and this is again a pulse transformer to transferring the pulse and it will count the number of the pulses. So in this way, you can count the number of pulses and also you can find out the speed of that gear rotation. So how much speed it is, this gear is rotating. You can find out with the help of the magnetic or variable reluctance sensors or VR sensors. So what are the advantages of the pickup, reluctance pickups? It has a low cost low weight and it is very robust. It can be used in the harsh environment and it also works in the high temperature. So that makes it ideal for turbine and in the internal combustion engine to measure the number of teeth and where there is a temperature effect or whether there is a high temperature constant is there. You can use this reluctance pickup coil without any compromising in the performance. So what are the disadvantages? Disadvantage is it is difficult to measure the low speed. If this gear is rotating at the low speed, it is difficult to measure that because the pulse separation will be the more as if the speed of this gear rotation is low. So that's why this is one of the disadvantages and of course it needs the additional circuitry to process the pulses. So this is one of the disadvantages. Now coming to the applications of the VR sensor or reluctance pickup coil or reluctance pickup sensors. So it will have application to measure the gear to speed and it has application of the major turbine speed. So as I explained it is working in the high temperature. So turbine at the high temperature it can work harsh environment also. And there are also many application it is also used in the musical instrument as a VR pickup coil. So these are the different applications of the reluctance pickup sensors or VR sensors. Next is the photoelectric pickup. So name itself are just a photo means a light and electric means electric is the voltage and the current is there. So in the photoelectric pickup is one of the type of setup which will converts that is light into the equivalent electricity. So this is one of the setup for the photoelectric pickup. So when there is a shaft is rotating again it is used for measuring speed. It is also used to measure the number of object also this photoelectric pickup sensors. And if you see when this shaft is rotating and at the at this side if you see there is a detector is there light detector may be the photo diode or photo transistor. And here is the light source is there may be the LED light emitting diode or laser source is there. So when this light falls when there is a holes appears in the path of the light so this this will get detected by this sensor photo detector. And it will detect the pulse. So every time you detect the hole it will detect the pulse. So in this way you can measure speed and other parameters also with the help of the photoelectric pickup. Now coming to the application as I told you the speed measurement and also it is used in the counting the objects. So if it also used can be used on the conveyor belt when there is object is moving you can count the number of object with the number of pulses. Now these are the applications of the photoelectric pickup sensors. Next is the linear variable differential transducer. It is also called as LVDT it is a type of the transducer which will converts the linear displacement into the equivalent electrical output. That is that is a voltage. And if you see the but this is what is the conceptual image of the LVDT. So there is one primary coil and there are two secondary coil. So to the primary coil main source is connected and at the secondary coil the your signal is get detected in the LVDT. So there are three coils in the linear variable displacement transducers. Now coming into the construction in the construction as I told you there are three coils. This is a primary these are the secondary two secondary coils. So to this coil a source is given and there is a core there which is a very high permeable core. So may be made up of the soft iron or any other material and these are the extra coating on it. So when this core the material used is the high permeable material and these are the coil switches of the high density coils a glass coated high density coils are used here. So this core is moving in this in this type of the construction. So this about the construction of the LVDT. Now coming into the operation. So there are three coils one is the primary and there are two secondary coils one end of the secondary coil is tied together and at the opposite end you will get the output of this LVDT. So to explain the operation of the LVDT it can be explained in the three cases. So when this core is at the center position which is also called as a null position. So in the null position what happens the even voltage and e2 voltage which is generated due to this coil one electromagnetic induction. So these two are equal. So when these two are equal you will get the whatever is the difference voltage at this two point is a zero. So that that's why it is called as a null position and when core is at the upper position that is upward position. In that case the more flux from the primary of this coil primary coil is linked to this coil that is this upper one coil that is the even voltage will be the greater than voltage e2 in that case. So this during the upward direction you will expect the positive voltage and during the downward direction e2 will be the greater than even you may expect the negative voltage in that case. That is that will be the phase shift of the AC input here. Now coming to the characteristics of the LVDT. So these are the characteristics of the LVDT. So this is corresponding to the null position as I explain you null position in the null position you will get the output differential output is zero. And during the motion either in the upward and other direction downward direction when you are counting the mode of that output not the phase shift. In that case in the mode output you will only interested in the only interested in the magnitude not the phase. So in that case you will get the output which is a linear. So that's why this device is called as a linear. So this is output which is linear again this is output which is a linear. So this output is corresponding to full deflection that is full reading or full scale value. And again this is output which is corresponding to the full scale value in opposite direction which have a 180 degree phase shift. So these are phase shifted of the 180 degree. Now coming to the question very interesting question what will be the maximum and minimum output do you expect from the LVDT. So think about it right on the piece of the paper. Well the answer is the maximum output is the mode of the either E1 or E2. Or it will be the output minimum output will be the zero. So minimum output you don't have a confusion about it. So minimum output is a null position that is this is your minimum output. And what is the maximum output is the maximum amplitude of the signal you may expect at this. So either mode of E1 or mode of E2. So this will be the maximum output and minimum output is zero. Now coming to the application of the LVDT to measure the load and pressure LVDT is used. It is used in the servomechanism for controlling purpose. Also it is used in the aircraft satellite also and it has an application in the hydraulics. So to control the to control have a control of the have a control in the hydraulic machines. So these are the different applications of the linear variable differential transformer or LVDT. So these are the references. Thank you.