A Circuit Board With A View: oscilloscopes from Keysight Technologies enable new insights in EECS teaching labs

SHARE:
October 5, 2020

A recent donation from Keysight Technologies includes 120 new oscilloscopes, in two cutting-edge models.  

Jane Halpern, Department of Electrical Engineering and Computer Science

When the in-person labs of MIT once again fill, the students of EECS will have a fascinating new set of tools at their fingertips. Thanks to a generous equipment donation from Keysight Technologies, the department has recently completed a renovation of its teaching labs with 120 new oscilloscopes whose advanced features will make exciting new experiments possible. “We used to have to transfer data from scopes to computers to analyze, but these scopes are so astonishing that you can sit and analyze the data while you’re working on it,” says Steven Leeb, professor of Electrical Engineering and associate director of the Research Laboratory of Electronics. “They also have secure internet connectivity, so they’re perfect for lecturing and teaching.”

If you aren’t one of Leeb’s students, a primer might be helpful. “An oscilloscope is, essentially, a TV for electronic wave forms,” Leeb explains. “When an oscilloscope’s probe tips touch the metal on a circuit board, they act in the same way as an EKG reading the electrical signals from your heart, and plot the waveform as a function of time.”

But the new oscilloscopes offer more than just display. “These scopes come with a thousand amazing built-in functions to give all sorts of figures and plots, for example a fast Fourier transform, which will tell you all the sine waves in a given signal,” Leeb explains. This type of function is critical for pulling apart the discrete frequencies involved in complex electronic signals. Leeb analogizes those complex signals to orchestral sound: “A whole pile of musical instruments can make a middle C, but they don’t sound the same because while they all have the same base frequency of middle C, they add on different sine waves. Say you have a tuning fork and an oboe. While the tuning fork has the purest and simplest sine wave, the oboe adds all kinds of different higher frequencies. Within the human voice, a whistle is a pure sine wave, but a full-throated ‘ahh’—even at the same note--adds other features. These scopes will expose those features; they can figure out all the different sine waves going on so you can isolate and recreate the signal.” One teaching experiment involves the creation of a small circuit board “piano”, played by touching oscilloscope probes to its individual keys.

Here, a Keysight InfiniiVision DSOX4154A Digital Storage Oscilloscope displays a Lissajous figure, created when one slower and one faster sine wave are plotted against each other in XY mode. At bottom, the student circuit board “playing” the sine waves is connected to the oscilloscope using two probes.

“These oscilloscopes are a fantastic upgrade for us,” says Manuel Gutierrez, an EECS PhD student in Prof. Leeb’s Electromechanical Systems Group, who has been designing new lesson plans for undergraduates just beginning to delve into electrical engineering. “The large touch screens make it easy for us to interact with and interpret waveforms, and added features like the built-in dual-channel waveform generators make them highly versatile.”

The students are especially likely to appreciate the scope’s capabilities when they are challenged to begin building their own electronic circuits, such as oscillators. “Oscillators are a staple of electrical engineering art—it would be difficult to make cellphones, computers, synthesizers, and lots of other products we love  without them,” explains Leeb. Like a pendulum, the oscillator moves back and forth at a given speed—its hertz speed—powering electronics much as a heartbeat powers a human body.

“Among many other advanced capabilities, these scopes create Bode plot graphs, which are a staple that students use to make oscillators,” says Leeb. “You can do a bunch of math to predict where a resonance is, but the scope helps you identify and verify that peak, which matters because even after you do all the math, you’re not 100% sure what’s going on until you check to ensure your model was a good one.” Thomas Krause, another EECS graduate student working with Leeb, finds that teaching is more effective with the scopes: “The scopes help emphasize what issues can come about when you build electrical circuits. We […] don’t really think about how construction or other unmodeled effects can impact circuit performance. A good scope visualizes the impact and makes this point very clear.”

Here, a Keysight DSOX1204G displays a Bode plot graph. The “electronic pendulum” creating the graphed peak is at bottom.

Gutierrez agrees that seeing the circuit board in action makes learning more visceral than a purely theoretical approach to circuitry: “We spend a lot of time teaching students how best to debug their circuits. There are many techniques that can be taught to help find and fix issues, but almost all of them rely on an oscilloscope. With this crucial equipment, we can visualize clearly what is going on in our circuits.” Even for advanced students like Gutierrez and Krause, the Keysight scopes have provided a new perspective on the finer details of circuitry. Krause notes, “I’ve been lucky to use one of the higher performance models, and it is the jewel of my workbench. The impressive technical specs of the scope such as bandwidth and update rate help me see properties of electrical signals that I might miss otherwise. This helps visualize circuit performance and troubleshoot issues.”

The Keysight gift is the latest in a long-standing tradition of generosity: in 2013, Agilent (a corporate precursor to Keystone) donated 100 oscilloscopes to the student labs at MIT, enabling half the labs to be refitted. Under the continued guidance of Chief Technical Officer Jay Alexander, the company has now contributed forty Keysight InfiniiVision DSOX4154A scopes and 80 Keysight DSOX1204G scopes, valued at approximately $1.2 million, thus completing the upgrade across all EECS teaching labs. This state-of-the-art equipment means better preparation for the students starting out on their EECS journey—and the scientists and engineers they will become.