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- The multimeter is a great tool for examining and debugging circuits but it does have its limits. It only gives me a single number for the voltage I'm measuring at that moment. For circuits that only have constant voltages that's usually fine, but as I start building more complex and interesting circuits those circuits will have voltages that change over time. These changing voltages are called signals when they're used to convey some sort of information, such as an audio signal playing music on a speaker. As an electrical engineer I need a way to view the signals within my circuit and I can do so with an oscilloscope. An oscilloscope is a device that lets you view how a voltage changes over time. It displays the measured signal on a graph with voltage on the vertical axis and time on the horizontal axis. This will give you a critical view into the behavior of your circuits to determine whether or not it's working correctly, and it'll help you to locate problems within your circuits like sources of unwanted signals called noise. Trying to debug a circuit without an oscilloscope is like driving a car with blinders on, you can't fully see what's going on around you. Unfortunately oscilloscopes are quite a bit more expensive than a simple multimeter, but if you're going to be working with electronics you really need an oscilloscope, so getting one is a worthwhile investment. There's several things to consider when choosing an oscilloscope. First of all, do you want to buy a new or used one? You can save some money by buying a used scope, and there are usually quite a few listed on websites like eBay. If you do plan to buy a used scope online make sure that the seller indicates that the device is fully functional so you don't just end up buying someone's old broken lab equipment. The next thing to consider when narrowing down scope options is whether you want an analog scope or a digital scope. You can recognize analog scopes like this one because they display the measured waveform on a green cathode ray screen, whereas digital scopes like this one use a more modern LCD screen. If you're on a tight budget you can usually save some money by purchasing an older used analog scope, however they're much more limited in what they can do compared to their digital counterparts. Almost all new scopes being manufactured these days are digital, and thanks to advances in computer technology the price of digital scopes has come down significantly in the past few years. So my personal recommendation is to get a digital scope because of the many additional features they provide. A few other factors that you'll want to consider include the number of channels that the scope can measure and display at the same time, and it's useful to measure and compare signals at the input and output of a circuit, so you'll want a scope with at least two channels. Upgrading to a four channel scope is nice to have, but not necessary. Bandwidth is a key oscilloscope characteristic which specifies the range of frequencies it can reliably measure, and I'll show you the effect that bandwidth has on signals later in this course. For most common uses I recommend a scope with somewhere between 10 megahertz and 100 megahertz of bandwidth. Finally, if you're buying a digital oscilloscope you should also pay attention to the sampling rate, which describes how many times per second that signal is measured. I recommend getting a scope with at least 100 megasamples per second. There are quite a few brands of oscilloscopes on the market. Tektronix, Agilent, and HP are some of the more well known high-end brands. For my own personal projects at home I use this Rigol DS1054Z. It's a digital oscilloscope that has four channels, 50 megahertz of bandwidth, and a sampling rate of one gigasample per second. It also provides a lot of digital features like math processing functions and the ability to record signals to view later. I chose this scope because it provides all of the functionality I need for my hobbyist electronics and it was reasonably priced. If you're new to electronics, getting a scope like this one should serve you well.