How To Design A Low Cost Probe-Oscilloscope

[Mark Omo] sends in his write up on the design of what should hopefully be a sub-$100 oscilloscope in a probe. 

Many problems in engineering can be solved simply by throwing money at the them. It’s really when you start to apply constraints that the real innovation happens. The Probe-Scope Team’s vision is of a USB oscilloscope with 60MHz bandwidth and 25Msps. The cool twist is that by adding another probe to a free USB port on your computer you’re essentially adding a channel. By the time you get to four you’re at the same price as a normal oscilloscope but with an arguably more flexible set-up.

The project is also open source. When compared to popular oscilloscopes such as a Rigol it has pretty comparable performance considering how many components each channel on a discount scope usually share due to clever switching circuitry.

The probe is based around an Analog Devices ADC whose data is handled by a tag team of a Lattice FPGA and a 32bit PIC micro controller. You can see all the code and design files on their github. Their write-up contains a very thorough explanation of the circuitry. We hope they keep the project momentum going!

Review: Digilent Analog Discovery 2

I recently opened the mailbox to find a little device about the size of White Castle burger. It was an “Analog Discovery 2” from Digilent. It is hard to categorize exactly what it is. On the face of it, it is a USB scope and logic analyzer. But it is also a waveform generator, a DC power supply, a pattern generator, and a network analyzer.

I’ve looked at devices like this before. Some are better than others, but usually all the pieces don’t work well at the same time. That is, you can use the scope or you can use the signal generator. The ones based on microcontrollers often get worse as you add channels even. The Analog Discovery 2 is built around an FPGA which, if done right, should get around many of the problems associated with other small instrumentation devices.

I’d read good things about the Discovery 2, so I was anxious to put it through its paces. I will say it is an impressive piece of gear. There are a few things that I was less happy with, though, and I’ll try to give you a fair read on what I found both good and bad.

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