 Welcome to the session. So today's topic of the discussion is the strain gauge and load cell which is under the transducers. So my name is Ajit Subha Suryanshu, working as an assistant professor in electronics and telecommunication department in the Wachin Institute of Technology Salon. So what is the outcome of this student session? At the end of the session, students will be able to select the appropriate transducers, which is to measure the physical parameters, so like a strain and load. So what is before proceed further into this session of what is the basic knowledge you require? So first of all, you need a basic electrical circuit analysis to solve the electrical circuits and you should have a knowledge of the different materials and it is especially the electrical property, not a physical property. For examples, so the different types of the materials, if you divide it into the electrical it is the insulators, metals, semiconductors. So at least you should have a basic knowledge of the electrical properties of it and it is how the resistance changes with the change in the materials. So strain gauge, so what is in by the strain gauge? So strain gauge is a type of the transducer, which converts the strain into the equivalent electrical current or voltage. So again, the strain gauge is type of the electrical type of the transducers. So in the last session, we discussed there are different types of the transducers, electrical mechanicals and in the electrical mechanical, so this is one of the type of the electrical transducer, which converts the physical parameter into the electrical quantity. So there are two types of the strain gauge. So first is a wire type of the strain gauge and other is a foil type of the strain gauge. Now you can see these two diagrams, which is the foil type of the strain gauge. Nowadays, a wire type of the strain gauge is not used. First of all, it is construction, construction cost and second is the second is the sensitivity. So foil type of the strain gauge is a highly sensitive as compared to the wire type of the strain gauge. So this again, you can see these are the made up of the metals and which are the materials used commonly in this type of the strain gauge is the constant and different alloy with the constant. So this property of the material allows it used in the strain gauge. Now this two end, you can measure the change in the resistance. So this is a foil type of the strain gauge. Now working principle, so when strain gauge is under foil type of the strain gauge is under tension and under the compression. So when it is under a tension at this two end, you can see that there is a change in the resistance and when it is under a compression, you can see this the resistance change at this two end. So when you have a change in the length by law of resistance. So if you have studied in the type of the metals, when the resistance of the material or resistance of the metal changes with the change in the length and change in the cross sectional area. So when particular metal or material when it undergoes the physical changes, it will change its resistance. So in the first cases, under tension, you will get the higher resistance and the second case you will get the lower resistance due to the compression because the resistance is directly proportional to the length and inversely proportional to the cross sectional area. Now gauge factor. So what is meant by the gauge factor? Gauge factor is actually used to measure the sensitivity of the strain gauge. So to measure the sensitivity of the strain gauge, it is a ratio of the change in the resistance divided by change in the length. So if you take a ratio of the change in the length, it is nothing but the strain and it is a ratio of the change in the resistance. So what is the del L? Del L is the change in the length due to a compression or tension and L is the original length of the strain gauge. Again what is del R? Del R is the change in the resistance due to the change in the change in the length or change in the change in the lateral length or change in the collateral length and this these are the ratios of the resistance and this gauge factor is without taking the temperature into the without taking the temperature into the account. When you take a temperature into the account, you have to take this alpha. So this alpha is actually it is dependent on the material. So which type of the metal or material you are using in this strain gauge. Now strain gauge measurement. So it can be measured. So you when you connect the strain gauge in one arm arm of the piston bridge, you can measure the strain of that particular strain of that particular strain on that particular object. So when you connect a strain gauge in one arm one arm of the piston bridge. So what happens when the piston bridges get unbalanced, you'll get the you'll get the voltage at this two and so you can measure the current or you can observe the current at this two and with the help of the galvanometer or ammeter. So Whitstone bridge if you see the working principle of the Whitstone bridge, Whitstone bridge is in the balanced condition when opposite resistance. So this multiplication of this opposite resistance are equal. So this is a balanced condition of the Whitstone bridge and when this one of the resistances get changed due to change in the length or change in the due to the deformation in the strain gauge. So resistance changes this balanced condition is get changed and when this balance condition get changed you'll get the current in the galvanometer or voltage at this two and so which are the applications of the strain gauge. First is the component testing in the aircraft to detect the there is there any structural damage. Of course it is used to measure the strain and it is also used to measure strain or strain generated by the different machinery in the industries. So these are the application of the strain gauge load cells. So what is the load cell? Load cell is one of the transducer which will converts the force or load on it into the equivalent electrical quantity. Now we come to the conclusion that load cell and the strain gauge both are the electrical type of the transducer. So whatever the physical parameter for changing on it, it will convert into the equivalent electrical quantity. So which are the different types of the load cell? Hydraulic is the one of the type of the load cells, pneumatic type of the load cell is and last one is the strain gauge type of the load cell. So there are three types of the load cells are there. So we are going to discuss the strain gauge type of the load cell. So in the strain gauge type of the load cell we are using the strain gauge to measure the load. Now as you can see this construction of the load cells. So this is your load cells and on the load cell there is a foil top of the strain gauge is connected. So this is a foil top of the strain gauge is connected and at this end a load is applied. So when load is applied what happens? This strain gauge is under get compressed or which is under tension. So other end of this load cell is fixed and at the other end you are applying the load. Same here in this construction if you apply load on this top or on this if you place on this if you reverse it and if you apply the force on bottom side what happens? The strain on this strain gauges changes and you can measure the particular load or force. So now this is a working principle of the load cell. So one end is fixed, other end we are applying the strain. So what happens when you are applying the strain here? So this part is under tension which is in under compression. So when you connect when you have a foil top of the strain gauge is placed at this two end. So one type of the foil top of strain gauge is here and one more type of the foil type of the strain gauge is here. So there are four foil top of the strain gauge is placed at this four different places. So when you apply a load here so this type of the foil type of strain gauge is under compression and this is under tension. So again this is under compression and this is in the tension. Again working principle same as that of the strain gauge that you have discussed. So now this type of this strain gauge is connected to the one arm of the Wheatstone bridge to measure it into the equivalent electrical currents. Now my question is to use the can you measure a small weight in the milligram with the load cell? If yes can you give the examples of that? How you can enhance the sensitivity of the load cells? So I will give you a hint of the one hint that is if you connect more load cells here more strain gauge here you can enhance the sensitivity of the load cell. Can you give another example that you can enhance the sensitivity of the load cell? Think about it pause this video and write the answer on the paper. Which are the applications? Of course weight measurement is one of the application. Hopper scale is one of the application which is used in the districts and these are the different weight measurement applications are there in the airport to measure the weight. So these are the over end and again to measure the weights of the agriculture products. So all these are the applications of the load cells. So these are the references. Thank you.