 So, let us get started the intent of this discussion session is to allay some of the concerns that a few of you have raised what is happening in this course, something is being discussed and you do not really know what is happening where this is going. So, the intent of this discussion we would not keep going on and on about it, but is to allay some of the concerns that you may have and also present a picture of why is it that we are doing whatever we are doing. So, it is intended to be an informal discussion. So, if you sit there passively saying, then the point of the discussion is not served. So, I am going to ask you first to whatever comes to your mind as a concern about this course feel free to air it, you can joke around a little bit, but the purpose is not to joke around. So, be witty, but be to the point. So, I am going to start with so that I think about 120 people here, I want 5 or 10 responses on concerns about the course or comments about the course and we are going to list all of them down. We are going to begin with one here, tell me your name first, I am Sanjith, you have to speak louder, my name is Sanjith, one thing about this course, I mean one concern would be that, I mean we observed in the labs that not all components were working and quite a few students lost their marks because of that. Okay, let us move on, I am going to just collect the concerns. My name is Sameer, I would also say that the breadboards are not working, so whenever we connect the circuit, you have to keep the IC pressed and you do not get the results easily. I mean I am asking for more, I mean these concerns are going to be there in any lab, okay, something goes wrong, something goes right, etc., but is this your only major concern if the breadboards are all working, okay, everything is good, is that what you are saying? If the breadboards work, then we will get to see what we are doing because we are not getting a feel of anything. Okay, so next guy. My name is Akshay, I think that the number of TAs in the lab are less, we do not get to interact much. We have got something about, yeah, go ahead, something about logistics, all these are things related to logistics. Sir, my name is Saurabh, sir last year many of the students… Do not heat up your name, your name is Saurabh. Saurabh. Yes sir. Okay. Sir, last year many of the students got A grade in this course because the course was new to them, basically the course was new last year. So this year what do you intend to do, basically in physics lab we had that if we had the enzyme correct, we would be getting good grades. So is this, what is the percentage that you intend for every lab and then the enzymes. So these are your main concerns, is it, I want some more concerns pertaining to the content of the course, okay, these are some logistical concerns I am not saying they are not important, in the larger scheme of things they are not important. My name is Skand. Skand. Skand. Yes. Sir, I have got a couple of concerns, firstly like in the first experiment and also in the experiments following, we used a digital oscilloscope which was basically just in ADC. So this was leading us, I mean this, it is not a very accurate thing like a CRO, if he is supposing set the time scale as something different, then again by sampling theorem we get a different waveform altogether. So you perceive the oscilloscope, not very accurate, is there what you are saying? Also like supposing I want to observe any waveform and if my time is not correct, that is I do not know the exact frequency of the waveform that I am supposed to sample and if I set a sampling frequency, let us say 10 times of what I am supposed to be looking at. So in that case I will be getting a different waveform which again makes sense but is actually having a different frequency altogether. Fine. So what is the second concern? Sir, and this other thing is like I am from electrical department and we are having very similar experiments in our own department also. Okay. Sir, my name is Swaroop sir. I just have one small thing like we actually do not know what is happening inside the circuit, what exactly, for example let us take IC into consideration sir, it has many components in it, what is the function of each component, I think at least I personally am not clear with it sir, the theory and basics are not clear for us. I just had logistical problems only as far as I know I mean I only had logistical concerns basically number of TA is less and we do not know the grading scheme properly, content I don't think I have any. Okay, pink, pink shot at the end. I think I am not very clear about the details of SHIPRA. I am not very clear about the electrical circuits and the working. Anybody else? Sir, my name is Urmil and I think that the lectures should be made more meaningful with a clearer objective, like we don't really need to attend these lectures to be able to complete our lab assignments, we just go there follow the instructions and walk out, it's not, we don't understand much, so if that could be improved. Is that true of all lectures? Most of them, like we don't go out saying we know, we learned something, it's just that okay we sat through it and that's it, nothing interesting or no application and stuff like that and they seem random. What do you mean by no application? What do you think is an application? Yeah, we did discuss little bit on it but it was not detailed or it was not enough. Okay, two more and then we will stop. So my name is Arshad. Some eager beavers are there. Arshad? Arshad. Spell it. H-A-R-S-H-A-D. Arshad? A-D. Okay. Sir, in this course we are learning small, small bits of a lot of things but what I'm wondering is at the end of the course what are we going to have gained exactly? Sir, I am Ankit. Sir, actually I have four concerns. Firstly, I challenge you that the four concerns will not be all different. It might be. First is, sir we need extra material, extra and well organized material. Suppose we can find material on net but it is not, we can't order them actually because suppose we are doing ADC, so I am just, my department is meta. I find it very... Slow, slow. You need extra material. Yeah, extra and well organized material. Extra and well organized material. Okay. Because I don't have enough knowledge of electronics so I find it very difficult to go through all the higher procedures. Okay. Second point is train TAs. Although it, I observed that in my whole class only two or maximum two TAs have full knowledge. Yeah, maximum TAs, no that has happened to me twice because in the second experiment that LED was not lighting up so I called two or three TAs. They all say okay, okay, okay and just right away they say I will call another TAs. Third point is... Have you ever thought anything? Yes sir. Have you thought anything to anybody? No sir. Try it. Try it once. Anyway, go on. I am not giving excuses but go on. Sir, suppose my one lab is incomplete. Okay. I can't complete it in... One lab is? One experiment has not been completed in three hours. I think that that person should be given extra time or should be called on another lecture because it's just a learning experience. We do not belong to other department so we don't have to rush for the CPI or so. We just want to learn that means we can take our time. Okay. Fourth is the... I think that it's a flaw in grouping up our... That is our class. We all meta. We belong to meta. Okay. We all meta-vales. We all... Sorry. We all meta-vales are put in the same batch. So hardly anyone of us know about electronics. Electronics... What do you think knows? Yes sir. Who do you think knows about electronics? So I just... I'm asking you. You respond to that. Who do you think... I think that it might be electronics people. They surely would know... How many of your electrical guys are here? I just want to club these amongst us so that we can gain extra knowledge. I bet that that guy with two hands put up he doesn't know any electronics. Sir, there are exceptions always. There are exceptions always but it would be better. It would be a learning experience. So bunching of batches. Bunching of batches. So you want heterogeneity in batches? Yeah. Thank you sir. I am surprised that there is no question on the content. Nothing about the content. No concern at all about the content. I want just one or two concerns about content. I think we have enough... Enough cribs about the logistics and the way it is handled. I'm not saying you should not give logistics problems but we want some... It's because of content. I want only content cribs now. My name is Manasvi. Louder. Manasvi. M-A-N-S-V-I. Sir, the problem statement of the experiment is not very accurate, sir. So some of the TAs expect us to give the entire theory while some of the expect us to simply write the readings. So that's not very accurate. People end up doing different... And almost entirely different experiments. So can I say that the experimental write up needs to be... Should be more accurate, yes sir. So my name is Utsav. Saj Utsav. Utsav. Yeah. So I had this question like initially in the first lecture we were told that this course was more about why do we need experiment and what is like. But now I'm realizing that it's more of electrical circuitry rather than really getting to the depth of why we are doing this experiment. We are learning something but the spirit that it was initially introduced to us that is not the same. Okay. So we have quite a few cribs. Thank you for sharing them. You can also... I want one or two people if you have anything to say about what do you think is going right in the course. What do you like about the course? If you have anything to say. My name is Rahil. R-A-H-I-L. Rahil. Yeah. I like the fact that it's slightly vague. I mean I know it's contradicting with the first thing that it's not written very clearly. But I like the fact that it's vague because other labs that we have done in physics and chemistry they detail out everything about the experiment. We just blindly follow the procedure and that's what we do. Here we play around a little bit so I kind of like that. So some exploratory content seems to be there. Yeah. Or you think that there is some exploratory content. Okay. Only one more and then we'll start some discussion. But this is good. I didn't think that... How many? Four. Six. Ten. My name is Rahil. What I like about this lab is the format of it is like conducted. Because there's a lecture for describing what we are going to do. Also the best part is that we don't have to submit any journal. You don't have to? We don't have to submit any journal after the lab. Because logging everything in a journal was more of a mechanical thing. It was not helping any understanding. But the best part is that there's a lecture for the lab so that we can understand what is going on. Okay. So usually when you ask for... How many of you have seen Mouth Shut? Mouth Shut? Review? Never gone to Google and done a review? How many of you have read a review about anything? A restaurant? Movies? IMDB? Must have read, right? So usually reviews are all bad. You know why? Because the people who want to pour their hearts out about the review are the ones who come and write the review. Those who are happy don't write anything. So I'm not saying this is like that but usually it's like that. Okay, good. So let me start addressing some of it. I cannot address over here. It needs action from my side to make the time that you spend there more worthwhile. Which I will try and do. Okay, so logistics issues. Not all components working. Breadboard is not good. This is not a good thing as a feedback to us. There's nothing that we can discuss right now. We just need to get better components and breadboards. Okay, so we'll do that. TA training is an issue. I appreciate that you have raised it. I won't comment too much about the grading scheme because that doesn't seem to be like a major learning hassle. Oscilloscope is not very good. So let me ask a question. How many of you before this course had ever touched an oscilloscope? Physics lab. How many of you had never actually touched an oscilloscope but told that something is going on there and you see what is happening? Everybody knew what an oscilloscope was and what you can do with it before you came to this lab. I own up if it is no or I already know everything then say yes. Not very clearly. You know that something is there on which some squiggles are moving around. Okay, and maybe you can look at it and make sense. That is an assumption we started this lab with. Not everybody is on the same plane with regard to exposure to electronic prototyping equipment. Okay. You may deny it but I know from the look of what you do in your lab. Once in a while I come around that you don't really have comfort level yet. Not everybody has comfort level yet. Okay. So the yes the oscilloscopes that we use here are not fancy ones. Okay. The fancier ones you will get when you do more serious experiments. You will get access to it at different points in time in your during your course here. But I am going to challenge you that for most things that you are going to end up doing here or anywhere in life. This oscilloscope actually is going to suffice. Okay. It is certainly not as good as the textronics oscilloscope that you carry the CRO that you carry. But this one is as good as it can get in terms of providing you the learning platform. You are not going to get too much too many things that are better and more convenient to use. Things are coming on the screen and you can play with it and all that. Okay. So I am not too bothered about that comment. Don't know the details of circuitry functioning. I am just going step by step and then I will come back to taking stock as a whole. You will not know the details of the circuitry that are functioning because you are learning it as a black box. Now this is how you learn anything that is new. You need to have an overall picture first before you get into details. Suppose I came here, I know what the comments will be. Suppose I came here and started detailing the circuitry of an EDC in as much excruciating detail I want to. Half of you will run away. So if too much information is given too soon, that is also a problem. So from teacher's point of view, it is not a very good idea to give too much information too soon. Now that does not mean that you should not seek more information. If you feel that I know what it is doing from a black box perspective, but I want to know what is happening inside in more great detail, nobody is stopping you from learning it. Okay. We are happy that you have gotten to the point where you want to know more about what is happening. Okay. So I will come to some philosophical aspects of the introduction of this course itself. Lectures need to be meaningful. They seem random. No application. Okay. If you are saying that a lab course has no application, I do not know what you mean by application. Application are not introduced to you. The applications are not introduced to you. Okay. Fine. That is a concern we need to address. I am not saying we should not address, but I will come back to that also today. Lectures need to be meaningful. Okay. So one thing you need to get more and more used to is that you need to move away from this traditional pedagogical method that you have been introduced to. Some guy comes in front of you, lectures something, gives you some problems you solve, then some of them are right, some of them are wrong, you get marks for it. Okay. Now if you continue to operate in this mode, you will really not learn anything. Take it from me. Okay. Because you are putting the onus on teaching or onus on learning on the guy who is saying something. Do you understand what I am saying? You need to put the onus on yourself. Okay. That does not mean that the guy who is standing here has no role to play. But the role the person plays is actually far lesser than the role you play in your own learning. Okay. So one of the issues that a lot of people face is that you have been steamrolled in one direction for 12 years, 13 years of your life in one way. Don't open your mouth. Listen to what I am saying. Write an exam, get good marks. I mean that's the way you have been exposed to. Okay. All this, I mean this part of what we are trying to do here is to get you out of that. Because if you really want to learn something, you should have the interest to learn it. Not that I am coming in trying to make things meaningful. That does not mean that I don't do a good job of making it meaningful. But this is an issue that all undergraduates face during their lifespan as a student. Because that's the reason you are here. You are trying to make sense out of several things that seem to exist that you want to design, you want to build, whatever. So this will not come to you all of a sudden. I mean sometimes the lectures are held which may seem meaningful, sometimes they don't see meaningful. But you have to make sense out of it overall. Okay. We are only there to guide. Okay. So maybe that's an escapist answer but that's the truth. Okay. So this is this comment I like. Problem statement of experiment is not accurate. Experimental write-up needs to be improved. That is true. We really need to improve our experimental write-ups. And we are working on it in subsequent lectures. You will see that we will act on that. The spirit of the course is unclear. Now what happens is, I don't know if you remember the comment I mentioned at the end of the first lecture. I said something like, you will get drowned in some details, some ADC, DAC, sampling, a lot of details, I mean a lot of words thrown around jargon, you getting used to some circuitry, some forms of ICs, breadboards and a lot of things that are getting introduced to you. You will get drowned in the details. But if you are able to understand the overall spirit and link it up to the overall spirit. So we will discuss the overall spirit of the course once again and application. Somebody said application. So we will talk about some application. So you will need to reinforce the spirit for yourself. You can always come to any of us if you want to get re-oriented towards what is this course doing, why am I doing this experiment, for me to learn this thing, etc. Those are important questions, usually difficult to convey in lectures, but better through discussion sessions like this. So, Harshad, small bits of learning, big picture is unclear. So that's the point of this discussion, that we want to have a sort of big picture discussion. So we are not going to discuss ADC, I am not going to discuss all that. That you do in your labs. This is not the forum for that discussion. We will have a big picture discussion. What is it that we intend to do overall? Why did we do whatever we have done so far? That sort of thing. One thing I am not addressed is, what heterogeneity in batches? You guys are all the same. You may think you are different. There is really no difference between electricals and metas and civils and CAs or whatever. Hopefully the first lectures point got communicated and what you have done so far I will link up to the first lecture, what I said in the first lecture. So experimentation is an integral part of the scientific process. I mean scientific process has some steps. So first you make some claims, somebody makes a claim called a hypothesis. Then you construct a repeatable procedure, which is an experiment based on whose results you can conclude something about the hypothesis. Either you say the hypothesis is not invalid or you say the hypothesis is invalid. So the reason I have put not invalid is important. We will have a small discussion and then we will move on. An experiment can never conclude that a hypothesis is correct. It can only conclude that the hypothesis is not incorrect. The reason being that it may be that you may you have not observed something that somebody else will observe some other point in time. In fact, if a hypothesis does not lend itself to this sort of a scrutiny that it can be wrong. That is not a scientific hypothesis at all. That is the very essence of science that any statement you make is falsifiable. That is you can conclude that it is wrong through the conduct of an experiment. If you make a statement which you say is correct, that is not a scientific statement at all. It can be incorrect only then it is a scientific statement. So this is an important point. I do not think you will get this emphasized during the course of your life, but you need to understand this. At best an experiment can say that something is not incorrect because that is the way new theories get developed. Somebody observes something and says that this is my theory and that appears not incorrect for a period of time and then somebody observes something else and the theory is incorrect and the theory gets modified. That is the way things move on. So an integral part of this is for you to be able to construct a repeatable procedure to test if what people are saying is right or wrong and that repeatable procedure is the experiment. That is what was communicated in the first lecture. Now what does it take to set up a modern day experiment? Suppose you say that an integral part of the scientific process is experimentation. You need to understand what does it take to set up a modern day experiment. Because you are all supposed to be linked to science or engineering in some way. One part of it is to understand the hypothesis. You need to understand what is it that the hypothesis is saying. What should I do to say if the hypothesis is right or wrong? I mean that is some sort of analytical reasoning behind the hypothesis. One of the things that is critical is you need to find out what needs to be measured. In your repeatable procedure you need to measure things. You need to be able to find out what needs to be measured. For example, Galileo's hypothesis that we spent quite a bit of time on. In the first lecture says that a body gathers equal amounts of velocity and equal intervals of time and it is dropped from rest. That is a hypothesis. What you need to measure there is velocity. What you need to measure there is time. You need to understand that the variables you need to measure. You also have to have some sense of the sensing principle involved. I will come to that. I will ask you some questions in an application example that you see in everyday life. You may not be exposed to it, but it is happening in everyday life. The sensing principle behind the quantity that you want to measure. That you need to get a sense of. You also need to know where to put the sensor that is going to give you the information that you are interested in. So, installing the sensor at an appropriate location. Once the sensor is installed based on which you can obtain some measured information. You need to make sense out of what comes out of the sensor. So, you need to be able to process the data that comes out of the sensor. And you need to later on post process it and make sense out of it of the data. All our attention so far in this course. So, does this look reasonable first of all as the set of things that you need to be able to do. Any person who is conducting an experiment needs to be able to do. If you are going to construct a reasonable experiment. I do not think this is unreasonable. Anybody thinks this is unreasonable something that has been missed out. So, all our energy so far have been focused on bullet number 4. Processing data from installed sensing. The reason for this is that is of a because of a historical baggage that we have all gathered. Most people in India who are so called engineers cannot measure anything. They look at some display which says some number and they write the number down. That is not measurement. Asking critical questions about what you are measuring. What is the sensing principle? Where have you installed it? What is the data that is coming out of it? What is the form of it? How do I need to process such that I can make sense out of it? How do I calibrate my sensor? These are mature questions that most people are not exposed to at all. And if you want to be able to process data in the modern day world in a fashion that is mature. You have to be exposed to electronics because it makes your job so much easier with regard to post processing. That is the reason why there seems to be an inordinate emphasis on instrumentation electronics. Everything that you have done falls in the bullet 4. You will do bullet 5 during the course of your projects. You will do bullet 2, 3, etc. in the latter half of this course. Or at least understand what needs to go into 2, 3. So, in the context of what you need to do to set up an experiment. I hope what we have done so far sort of falls in place. We are learning how to process data from installed sensors. That is what you have done so far. Now the process data comes in various forms. Or the data from sensors comes in various forms which you need to process. So, you need to know if the data comes in various forms. You need to know what forms it comes in. So, let us think of a class 7 student. When were you exposed to the notion of real numbers? Real numbers. Class 13. Class 6 you were exposed to real numbers. Class 6 you were exposed to real numbers. So, there are a lot of different types of numbers. You know that now. These are all constructed by human beings. Natural numbers, whole numbers, real numbers, rationales, complex numbers. What else? Other things that you have been exposed to. So, unless you know what form they take. You cannot really work with them. This is very similar to that. You need to be exposed to different data of different forms. Unless you are exposed to that. If you are presented with the situation that you have not encountered before. You do not know what to do. You will again say that I do not know what to deal with this. Most people have this difficulty. For the first time you are exposed to rationales. In fifth standard, I think I remember rationales fourth or fifth. Something like that I was exposed to. It took some time for people to get used to it. Some fraction there, some 2 by 4 is the same as 1 by 2 and something the teacher used to say. So, all that it needs some exposure. You are doing the same thing with a different set of things here. You need exposure to things that you need to get used to. So, that learning curve hopefully will be steeper. You will not take 4 or 5 years to learn something. But that is the reason why you have been exposed to different sorts of data. How do you process different sorts of data? What goes behind processing? Now, I am going to talk about an application example. Somebody says no application. You are all engineers or wanting to be engineers. You do not know any application. So, the application I am going to throw at you. Let us see how you perform. So, this is a schematic, an abstract view of an engine. What do you see in the middle? This guy is where some fuel and air mixes, spark is ignited, something burns, something piston moves. Then you generate an energy that you run your vehicles with. This is there in every car, every motorcycle, every 2 wheeler, 3 wheeler. Now, you may not know it, but every car has fairly sophisticated electronic controls in it. Decisions are made in real time, real time meaning as and when things are happening. You understand what real time is? So, if I am talking to you and you are responding to me with an acknowledgement, you are hearing something, you are responding to me in the time frame that I am comfortable with, then you are responding in real time as and when things are happening. As opposed to I say something, you do not respond at all and then 5 weeks later there is a response. That is not real time. So, lot of things are happening in real time. Decisions on how much fuel to put in, when to put in, when to spark, all these decisions are being taken by a computer sitting in your car. So, for it to make these decisions, it has to measure different things. So, I am going to ask you to suggest how different things are measured. All the red lines that you see, do you see some red lines here? Red, blue and green. Red lines are all measurements, quantities that are measured. One of the things that is measured is the position of the crank. You know what a crank is? The gold chakras that is below the piston. So, when the piston moves up and down, the crank goes like that. How do you think the position of a crank is measured? Shaft encoder is one way, but that is not what is used in cars. Shaft encoder will not survive more than few tens of thousands of cycles in that environment. How do you think the position of the crank is measured? Pot. Can you use a pot to measure a position of a crank which is going some millions of cycles turning around? How will a pot do it? It is ok, you can throw anything you want. So, crank position measurement. Some suggestions, one guy says shaft encoder. How many of you know what an encoder is? You do not know what an encoder is. I will describe it. Some other guy says potentiometer. Any other suggestions? Some words that you might have heard. Sonar. Radar. That is also used in submarines. Lagavna or laser. Ok, anyway. So, we are going to have a little bit of a discussion here. These are not irrelevant choices. You know how a potentiometer works? Have you used a potentiometer so far? How does it work? What is its principle? Variable resistance principle. So, basically it has three terminals. You have a resistor and three terminals. And depending on and you have a moving terminal. Ok. So, the resistance between the moving terminal and any one fixed terminal keeps changing depending on the position here. Ok. So, by measuring the resistance in some way you can know the position of this wiper. Ok, that is how a potentiometer works. It is like a rheostat. You must have used a rheostat in school. Did you actually do a rheostat experiment in school? Somebody said. Do not do that. It is done. Then you will get a mark. You did a rheostat experiment in school. So, the potentiometer is a rheostat. It is just that it is not so bulky like a rheostat. The rheostat is a linear device. This is a rotary device. Ok, so the wiper goes through some spiral. If you open a potentiometer you can see a spiral. So, that is the measurement principle. It is variable resistance. How does a encoder work? That is exactly the reason why we are exposing you to some other stuff that may not seem directly relevant to measurement. But you need to be exposed to it. Ok, so the way a shaft encoder works is very simple. So, you can think of a disc. This disc is mounted on a shaft. It rotates along with a shaft. I am just giving you a crude description of a shaft encoder. Suppose the disc has been divided into a lot of different sections. Ok, some of them colored white. Some of them colored black. Let us say alternately. Explain the principle. Now, if you shine light from here. Plect it lesser than the white. Then if you have a detector here which says that I will detect the reflected light. What comes out? Depending on the intensity. I decide how many blacks and how many whites have passed in front of me. Then I can count that for one revolution I should have. If I know that 5000 whites and blacks should have gone. And 3000 of them have gone. Then I know it is 3 by 5th of a revolution I have moved by. So, this is through the counting of lines or blacks and whites that pass in front of it. That is how this thing works. This measurement principle is similar to what? Any other measurements? So, anyway I will just call it optical. This is an optical encoder. Older form of optical encoder used to work like this. So, the point I am trying to make is that in order to be able to measure something. You need to know such details that we have not yet come to at all. So, this is a variable resistance. This is a measurement principle. This is an optical instrument. What comes out of it after the measurement is also important. By the way neither of these is used for measuring crank position in an engine. So, I am going to describe that also crude thing it is, but it works. So, you have what is called a cogged wheel. So, basically wheel with some projections like this. Then you have a inductive pickup, inductive pickup. You know the principle of electromagnetic induction, right? B L V B I L, there are a problem. I will just refresh your memory. This diagram will refresh your memory. This is diagram. Make battery read although some velocity V. This is J E diagram, typical J E diagram. Another J E diagram is this and do some nonsense is that, right? Find all accelerations. So, this is related to this J E diagram. How is it related? So, when this thing rotates, ok? Suppose I just for the sake of argument I tell you that these fellows are some magnetic material. And I just put two fellows that are sticking like that in the presence of this magnetic material. What will happen? Two conductors. What will happen? And why? The physics problem solved. Force is equal to B I L and all induced TMS is B L V. Somebody is saying flux, good change in flux of what? So, this the gap between this guy and this guy sees a change in flux, magnetic flux, ok? Because sometimes this cog is there, sometimes it is not there. So, if you place a conductor in a region of changing flux what happens? And you can close the circuit. Current will flow, but why does the current flow? Because there is some fantastic phenomenon, some induction, some voltage is produced. Nobody knows why, it is just produced, ok? Which is proportional to the velocity or which is proportional to the rate of change of the flux, ok? So, what will happen here? Suppose I look at the voltage across this guy. How will my voltage look? Periodic if it is rotating with constant velocity, but how will it look? Do not be scared, I mean this is all stuff that you are supposed to know. If you giggle away there, you are not going to be able to answer the question. How many of you have nothing to do with, how many of you think this has nothing to do with this problem? How many of you think this situation has nothing to do with this problem? Conductor moving in a magnetic field with velocity V and all that. You are scared, I know that many people know, think that there is nothing, ok? So, this is the principle of measurement that is used to measure the position of this cog, ok? So, how does it look? I am just suggesting something. When the cog passes in front of it, right? There is a change in the magnetic field, magnetic flux because of which there will be a spike. When the other part of the cog, when this part of the cog comes in, let us say it is rotating like this, there will be a spike, the other part of the cog goes back, there will be a spike in the other way, ok? Maybe there is something in between, it looks like this. So, let me redraw it. Without understanding, without knowing too much about what is happening, I can draw something like this. This is how the voltage across this guy is going to look like. If I plotted it as a function of time, how many of you are not understanding this at all? How many of you do not understand this at all? So, let us look at this part of it. Let us say there is some flux density, voltage is induced only if there is a change in the flux density, right? So, when this magnetic material comes in, so this is rotating, this part was in front of this guy. This edge has come in front of this guy, changes the flux density because of which some voltage is induced. You said you do not understand what is happening, what is the direction of the flux? High level question. You figure that out, which direction it has to be in, ok? Suppose it is in the right direction, some magnetic material is there with the right direction flux. Do you realize that when this edge comes, there is a change in the flux? Similarly, when this edge comes, there is again a change in the flux and then here it remains constant. Again a change in the flux, again a change in the flux. So, this part is when this part of the teeth is in front. This part is when it goes up and when it comes down. So, what I am going to do is I am going to post experimental data from a sensor on the website. Actual sensor that is used in cars and motorbikes and all that, ok? You will see it is not very different from this. It will be very similar to this. What did it take us to draw this? To understanding qualitative aspects of the physics involved. How much this is going to be, etcetera that we do not know, magnitudes. But qualitatively all we need to know is some understanding of electromagnetic induction, some flux changes and therefore some voltages induced. Now, this is the voltage that gives you idea of one cog passing in front of it. And by counting the number of cogs and knowing how many cogs are there for one revolution, you can you know approximately the position of the crank in its in its revolution. If you have a large number of cogs, you will have more resolution, right? Yeah, that is all that is required. The same what you are referring to is an incremental encoder. You can also have an absolute encoder. What he is saying is that you will not know whether you are in this cycle or in another cycle, because this is going to repeat itself, ok? That is true, but even within a cycle it is important to know what the position is. The reason being is that when you spark is related to the position of the piston. You should not spark randomly, ok? That is the reason you need to know most of the time what the position is. So, what you do is you leave some part of it open, ok? Which comes when the piston is right on top, let us say. And with respect to that, you will know how many cogs have passed and how many degrees have happened, etcetera, ok? Anyway, so the point I want to make is that this is the sort of waveform that you will get voltage as a function of time, ok? What you need to know from this is the position or how many cogs have passed. That is all I am interested in. So, I need to be able to process this data suitably, present it to a brain, which is the microcontroller. So, I need to know two things. How do I process this data and what does the microcontroller accept? What does the brain accept, ok? That is what you have done or you are getting exposed to in the first three labs. In the next lab, you will get exposed to the microcontroller, a microcontroller. So, that will give you some idea of how do you process signals to put it in a form that is acceptable to a microcontroller, ok? This is a skill set. It is not conceptual. These four labs are not very conceptual except the idea of sampling, sampling theorem. There are some conceptual elements, but largely it is a skill building exercise and building familiarity, ok? One thing you will understand, hopefully, if ever you think about this course, after this course is done, you will not be scared of new situations that come up because ultimately you need to know, ok, tell me what the form of the data that is and I need to know the circuitry that will lead me to interface it with the microcontroller. That is the way you need to think. Exactly what the circuitry is going to be, you may not be able to design it, but you will be able to look around and find out that, you know, I need to be able to use these things and go to people who can design it or just buy and use. But at least you need to know that you need to process data to make it palatable to a digital computational device, microcontroller, ok? That is what you have been doing. So, example of application of why you are dealing with analog signals. This is an analog signal needs to be converted into something which is accounting signal, right? So, for that you need to be able to use ADCs. Maybe you need to be able to use some other devices if required, ok? So, that is the reason why you have been exposed to whatever you have been exposed to, ok? So, this is about crank position measurement, ok? I am not going to bore you about everything that is there here. So, you see something called the exhaust gas oxygen sensor, ok? This tells you the content of the content of oxygen in the exhaust. By the way, this is there in every car. You do not know it, but it is there in every car. How many of you know this? Tell me what is the exhaust gas oxygen sensor do? It measures oxygen content. So, the way it does, the measurement principle is very different, ok? It is the diffusion principle, ok? So, you have, you must have learnt about osmosis, right? You have a semi permeable membrane across widths from high concentration to low concentration, something flows, right? Process osmosis, diffusion, another process where you have a medium and something flows, goes through a medium, right? So, you have oxygen on this side. So, this is the exhaust, exhaust pipe and this is atmosphere. This is exhaust gas. If there is an excess of exhaust gas here, you have a medium, ok? Made out of some ceramic usually, which will allow oxygen to diffuse through to the atmosphere or the other way round, ok? If this is more oxygen, this is less oxygen, then it is going to go the other way. If it is this more oxygen, this less oxygen, concentration wise, ok? So, the, what you do here is that you have some electrodes. You have heard of the Nernst cell, right? Nernst cell, another J e, e naught minus 0.0591, something like this, right? By n log of some blah. So, this Nernst cell is actually working here. So, you have some electrodes across which there is a potential difference built up because of partial pressure difference. So, log is actually the ratio of the partial pressures, ok? So, all that is happening. So, this is a different principle of measurement. It is not variable resistance. It is not optical. It is a diffusion principle and then some Nernst equation involved there, ok? So, again what comes out of here because of this log? This log is makes something change drastically. So, what comes out of here is low oxygen in the exhaust, high oxygen in the exhaust. If you look at the voltage across these electrodes, it looks something like this. Switches, oxygen there, oxygen not there, oxygen there, oxygen not there, oxygen there, oxygen not there. That is the nature of this data that is coming out of the sensor. It will keep doing this if your control is good, ok? So, the nature is different. So, look at this and look at this guy. They are not the same. They look the same and they are not the same, ok? So, you should be able to process what comes out of this confidently and you will do that only if you are exposed to some electronics or you will know how to do that through somebody only if you are exposed to some electronics, clear? What about throttle position? Throttle position is actually a potentiometer in most. You mentioned something about a potentiometer. Throttle position is this guy that is what you move in your accelerator. When you press your pedal or when you do this in your bike, you are actually changing the amount of air that goes inside for the throttle position. That is measured because it is it does not keep turning. It only goes from one position to the other. Potentiometer works fine, ok? So, it is a variable resistance principle. The point I am trying to make is that what you measure for a variety of purposes, the data that comes out of what you measure takes different forms. You should be comfortable with the forms. You should be able to process those forms. Obviously, we cannot make you comfortable with all the infinite forms that exist, ok? So, give you a feel for the forms that exist. Make you ask the right questions. The first question to ask is what is the form that comes out? What is the form I need to make it into? If you at least know that you have to ask these questions in an experimentation situation, we have done our job because the rest of it I will know that you will figure it out, ok? It is not so much saying that this, this, this, this, all this has to be done, ok? So, in summary data from sensors comes in various forms. Comfort with various forms is essential if you want to become a good engineer. Computational ability in today's microcontrollers is such that you want to present it to microcontrollers so that you can do a lot of processing with it later on, ok? So, you have to be comfortable with, with data acquisition systems that utilize digital computational devices. So, this is all skill building, ok? So, with this background any questions on why we are doing what we are doing? Does it, does it look reasonable that we have to deal with ADCs and DACs because the form of what comes out is analog. You may want to convert it to digital because something accepts only digital. You may want to sample something because something accepts only sampling. In the process of sampling you may lose information, but you can reconstruct it through appropriate filters, blah, blah. So, those, that part of the background is required, ok? Any other questions? Otherwise we can close. This is to give you an idea of why we have done what we have done. What is going to come in the future? Of course, you need to get exposed to microcontrollers that will, that is coming in the next lab. Subsequent to which you will start doing measurement related stuff. You will start looking at issues like accuracy, resolution, repeatability, reproducibility, calibration. What is the notion of calibration? Very important notion. Most people do not understand it, ok? So, some of those notions we will try to bring out in a couple of labs and then one lab in which you are actually doing an estimate of G, acceleration due to gravity, where you have to construct something and you have to measure something, you have to time something and blah, blah. Clear? The structure of this course, why we are, why we are here? If you have any queries on, at this big picture level, feel free to always moodle. One of us will respond to whatever your queries are, ok? The intent is not to bombard you with all these electronics. Ok, some scary board with some huge number of things sitting there, some ugly looking things also, right? Some jumper, you know, how many of you have heard the word jumper before coming here? So, half the class has not heard. Now, how many of you have heard the word jumper? Ok, any other questions you can ask me two minutes, otherwise we will wind up. I will wait for, I will count down.