So when I was interacting with the engineer from Arrow Electronics that helps build these IIOT systems for customers around the country, I asked him a whole bunch of questions. One of them was, what do you want them to know? And he pulled out his drawing of what the hardware organization of an IIOT system looks like, I want them to know this. But he had other ideas and other learning outcomes, and we're going to take a look at some of those. So we're going to look at a thermistor, which is a way to measure temperature. And he wanted to make sure that you understood how to calibrate a thermistor, how to filter, and how to sample it appropriately. So that's today's lecture material. And then on Thursday, we'll get into how block and object drives function. Understand how hard drives and solid state drives differ in how they operate. Grasp how traditional file systems fail to meet the needs of large data sets, operating on large data sets. And we'll look at the NFS, the Network File System, the Hadoop file system, and the Lustre file system. Sensors, one of the key skills to acquire, one of the key learning outcomes for this course is understanding sensors and how to calibrate them, and filtering when required. Not all sensors need to be filtered. It depends on the application. So I concocted kind of a cartoon example here, but it gets the points across. So we can talk about it, and you can take this knowledge with you. So we're going to look at temperature sensors specifically, as I said. Temperature sensors come in a number of different types. There's thermalcouples. They're very, very accurate. There's resistive temperature devices I personally don't know much about. These, I've had some exposures to thermocouples in my career. And thermistors, that's what we're going to focus on for this evening. A thermistor is a 2-wire device that changes its resistance as a function of temperature. And they have temperature ratings and temperature ranges, shouldn't come as a big surprise. I completely made up these numbers. A thermistor might be rated from -40 to +200 degrees. And its resistance at -40C might be 220K ohms, and at 200 degrees C, it might be 10K ohms. Could be, [LAUGH] someone could make a device that operates like that. So in many ways, it looks much like a resistor. This is a axial lead one, there's probably surface mount ones as well. Some of these devices have negative temperature coefficients. So as the temperature increases and gets hotter and hotter and hotter, the resistance goes down. And the manufacturer will provide you with a data sheet. And you'll have all the information that you need about how this particular thermistor operates, whether it's a positive coefficient or a negative coefficient thermistor. All kinds of information in there. Here's a positive coefficient, temperature coefficient, so the resistance on the y-axis goes up as the temperature increases. This one looks kind of like a sigmoid function. This one looks rather exponential. They can have different curve shapes.
