It works via the audio input, which is a decent A/D converter for signals in the audio range. The neat bit is that it can also get its input via a USB audio adapter hooked up using the iPad’s camera adapter kit. And I happened to have all the required bits lying around:
Woohoo – instant scope!
The horizontal and vertical are set with pinch-and-zoom, and the scale displays in the top left corner. Likewise, setting the trigger you just drag the red trigger line up or down.
Here’s a screen shot:
(it doesn’t quite come out at reduced size, but on-screen it’s gorgeous)
There’s also what appears to be an FFT power spectrum:
There’s also a (more expensive) app from ONYX Apps which can sample both audio channels and has a convenient auto-set mode (but no FFT):
The problem I have with all this is that the noise in my signal is gone. These samples were taken from the same 0.1 Ω shunt setup as in the previous days, so I’m not quite sure why the amplitude is different and why the signal is so noise-free. Perhaps there is some signal processing going in in the iPad.
But a real scope based on touch screen controls and such a large display sure would be phenomenal!