How to Perform Frequency Response Analysis on an Oscilloscope - Scopes University - (S1E6)

Today we're going to learn about what frequency response analysis is and how to set it up on an oscilloscope. Hi, I'm Erin East and welcome to Scopes University. In this episode we're going to learn a little bit about the basics of frequency response analysis. And the name itself is actually pretty self-explanatory. It enables you to analyze how your device is going to respond to various input frequencies. So, basically you input a sine wave of various frequencies into your device and then you compare and measure the gain and phase of the input of the system versus the output of the system. The result is a bode plot, which you may be familiar with, but a bode plot plots the frequencies on the x-axis and the gain and phase on the y-axis. The gain is just the ratio of the input voltage versus the output voltage and the phase is the phase shift seen between the input and the output. This will help you verify that your device is going to operate correctly when signals of different frequencies are input into the device. So, this is really useful to anyone working with amplifiers, filters, power supplies, audio systems, or anything like that and it's really convenient to have this tool built right into the oscilloscope because you can further characterize the device you're working with while you're already doing your other characterization on the oscilloscope. So, let's head to the lab to learn about the device we're going to be characterizing today and learn how to do that on the oscilloscope. So, for this exercise we're just going to build a very basic bandpass filter. This is made out of all passive components. All you need is a capacitor, inductor, and a resistor to build this. So you can really easily make this on a breadboard. And once I have this all set up on my protoboard, I can take a look at how to set this up with the channels on the oscilloscope. Most of the InfiniiVision oscilloscopes have this optional built-in frequency response analysis application and what it does is uses the built-in waveform generator to sweep a sine wave in a certain range of frequencies and then measure on the input and output of the device. So let's open up the application and the first thing I want to do is hook up the waveform generator to the input of the device that I'm working on. Next, we're going to probe channel 1 on the input of the device so we can measure the input and then we want to probe channel 2 on the output of the device. This will allow us to probe on the input and output and compare those. And we can see the first menu is the Setup & Apply menu. This is where you can configure the settings for the specific tests that you're working on and we can see here you can set up a frequency sweep which is most typical but you can also change the frequency mode to single just to test at a specific frequency. And this is helpful when you know there's a problem area in your device. You can also adjust the start and stop frequencies that the WaveGen will sweep between along with the source and the amplitude of the signals. On the touchscreen InfiniiVision oscilloscopes you can also specify the amplitude profile of the sweeping sine wave. Theoretically, the test amplitude shouldn't really matter since the gain is a ratio of the voltage input and the voltage output. However, when you're testing sensitive electronic circuitry, if the input test amplitude gets too high, then nonlinear distortions can sometimes occur during some frequency test ranges. So the amplitude profile allows you to optimize the input test amplitudes between different decades of frequencies in order to maximize the dynamic range of the measurement results without distortion. Once you have all of these settings configured properly for your specific test you can press run analysis. Now you can see the sine waves actually changing in frequency on the screen and then you can see each of the data points starting to be plotted on the bode plot as it runs. Then once it's finished running you can use the touchscreen to move around the orange triangular markers on the chart and you can see the data for these markers down here in the bottom right corner. The scope will already auto scale the bode plot when the test is complete, but to control the scaling even further you can press this arrow in the top right corner of the plot to change the scaling in the offset of both the gain and the phase. Lastly, you can also press this table icon on the left-hand side to see all of the data that we see plotted in the bode plot in an organized table instead and this can all be exported right into a CSV file that can be used for further analysis offline of the scope later on. One last thing, you can also select one of the rows in the table and a dialog box will pop up allowing you to run a single test at that specific setup frequency to do further analysis at that frequency point. So this can be really helpful if you see something that is abnormal at a certain frequency in your bode plot and you want to analyze that further and see what's going on at that specific frequency. The frequency response analysis application is also available on the low price 1000 x-series oscilloscope. So this is a lot of performance to get in this little scope. The features of the application are a little bit more limited, for example you can't set the custom amplitude profile, but it gives you the gain and phase data in the form of a bode plot on the screen so you're able to make these types of measurements on this class of an oscilloscope. You can see how convenient it is to have this type of analysis built right into the oscilloscope. You're able to do that frequency response analysis characterization of your device while you're already doing other characterization with the oscilloscope. And having that bode plot right on screen makes it really easy to see how your device is responding to various frequencies. Thank you everyone for joining me today. If you want to learn a little bit more about frequency response analysis and some more details of the application, make sure you check out the FRA datasheet, which you can find on the scopes university webpage. You have a link to that in the description below and you'll see it in a few seconds on the screen here. As always, just leave a comment below if there's a specific topic you'd like to see me cover in future episodes. Make sure you subscribe to our YouTube channel so you can continue to see more videos like this, and follow us on Facebook, Twitter, and Instagram.

Channel: Keysight Labs

Views: 45,320

Keywords: oscilloscope, oscilloscopes, waveform, voltage, current, tutorial, keysight, electrical engineering, computer engineering, electronics, digital storage oscilloscope, mixed signal oscilloscope, best oscilloscope, bode plot, frequency response analysis, agilent, rigol, tek, tektronix, lecroy, bandpass, low pass, high pass, filter, filtering, amplifier, how to, power supply, opamp, op amp, bode phase, bode gain, waveform generator, frequency response, frequency response analyzer

Id: ADmVAs6vqLU

Length: 5min 58sec (358 seconds)

Published: Wed Sep 20 2017