 Hey guys, it's Parker Dome, the longhorn engineer, and I'm going to talk about thermistors. A thermistor is basically a little device that as the temperature increases or decreases the resistance across the terminals change. You can use these to measure temperature and stuff on your microcontroller by converting this resistance into a voltage drop and then reading that voltage drop through an analog to digital converter and then, you know, calibrating your microcontroller and figure out what voltage, what temperature it is. But the bad thing is that as temperature increases or decreases linearly, the resistance does not change linearly. It's kind of like a nonlinear pattern, so it's kind of like this guy. So if we have temperature and then we have the resistance, gnomes, you kind of get a graph that looks like that. Now, if you're reading this into a microcontroller, you could just, you know, kind of do this. Kind of like do a linear interpolation, and so you kind of fake the, basically you return the thermistor linear between these temperatures and resistance, which is okay. I mean it gives you an okay result, but the better way to do that is to use a resistor bridge like we did in the last lab, the last video. And basically all you got to do is make a voltage divider, and so you have VDD, resistor 1, R2, ground V out. So what you do is you replace R2 with the thermistor. So the reason why this works in terms of converting this nonlinear pattern into a linear, because it's very easy if you just had this point, this point, and it was a straight graph, you could easily just read the value in and say it's that temperature. It would be pretty easy in terms of calibration because you only have to calibrate one point on your graph. So how this works is that this setup is also nonlinear, and so I'll explain that. We have V out equals R2 over R1 plus R2, and that whole thing times VDD. So if you graph this via R2, so R2 changes, you get something that looks like this guy. So you have V out and then resistance, you get something that looks like this guy. So as R2 increases, V out goes down nonlinearly. So what you can say about that is if you have this guy and then this guy, you get that guy, more or less. But that is the theory behind who will hand wavy theory, I mean there's some formulas that actually prove this guy. But that's the hand wavy theory of why we use a resistor bridge when using a thermistor.