How to Build an iPad Oscilloscope
To build an inexpensive touch-screen oscilloscope, start with an iPad
Photo: James Turner
It is a truth universally acknowledged that an engineer in possession of a good fortune must be in want of an oscilloscope. You can get low-end oscilloscopes for less than US $500, but they're heavy and cumbersome, and usually offer a minimum of functions, all accessed from knobs and switches.
Luckily, a new option has emerged for the scope-hungry hacker: the Oscium iMSO-104. For a mere $300, you can get this four-channel digital, one-channel analog touch-screen oscilloscope with some advanced trigger functions, handy calculations such as the signal root mean square or duty cycle, and the means to capture screen shots with the press of a button. Best of all, it weighs a scant few ounces and fits in your pocket with enough room to spare for an iPhone. The catch is that you'll also need that iPhone—or an iPad or iPod Touch—to use it.
But the software is free at the app store. Once it's downloaded to your iOS device, plug the iMSO-104 into the docking connector on the bottom and you're ready to capture data. Although it will work with the iPhone and iPod Touch, to truly enjoy the experience, an iPad is the way to go. Everything is controlled by touch. You can change the analog scale or time scale with a simple pinch of the finger and drag cursors and analog triggers around to measure the distance between two peaks or a voltage drop. You can trigger on an analog voltage level or use the digital probes and trigger on a rising or falling edge—or combine two digital signals with an "and" or "or."
I've been using logic analyzers and oscilloscopes on and off for 30 years. In terms of sheer ease of use, this is the best I've ever gotten my hands on (pun intended). But that's not to say there aren't a few caveats. For one thing, it's a 5-megahertz scope, so you won't be going out and taking test readings on microwave transmission signals with it. It is also somewhat limited in the analog voltage it can handle, maxing out at 40 volts in 10x mode and at 13 V in 1x. But within those restrictions, it's a great value and a joy to use.
So the next time you're hanging around the hackerspace and someone whines about not having an oscilloscope, whip out your iPad and iMSO-104 and give him an eyeful of signal.
This article originally appeared in print as "Scoping Out My iPad—Oscilloscoping, That Is ".
About the Author
James Turner is a contributing editor for O’Reilly Media and a correspondent for the Christian Science Monitor. Last year he showed readers how to build a digital microscope.