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Al Williams

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Scoping Out

March 27, 2010

Software and hardware have at least one thing in common: you really can't see or touch what's going on. When you are, say, building a house, you can "eyeball" what you are doing, but electrons and program flows aren't visible to the naked eye.

For software there are many tools for looking at what a program is doing ranging from debuggers to in-circuit emulators. For hardware, the tried and true answer is the oscilloscope.

My first scope was an RCA with a round tube meant for TV servicing bought at a hamfest (a swap meet for amatuer radio operators). Since then I've used a few dozen instruments of various types. Today I own a fine Tektronix scope, but I find I don't use it as often as I used to.

There's nothing wrong with the scope, mind you, but I've become more dependent on an inexpensive Velleman scope that connects to my PC. It doesn't have nearly the specifications of a high end scope, but it stores data and -- most important for me -- makes nice screen shots I can include in articles or reports. It also does spectrum analysis and can compute all sorts of interesting statistics on waveforms.

One thing I don't like about the scope, however, is it requires a PC. I have an old laptop that is pretty much just the "scope PC." The whole thing is portable but awkward. I also have coaxed the scope (a parallel port model) into working on my modern Linux box, but that was a trick and is hardly portable (I have a liking for big server cases and multiple monitors). Other PC-based scopes (like Bitscope and the Hatek models you see on eBay) also expect a PC.

I guess I'm not the only person who thought about ditching the PC. I recently ran across ScreenScope. You plug in a monitor and a mouse and you are set. A 50MHz scope with dual trace. About the same sort of specs on my Velleman, but no where near a big "pro" instrument like my Tektronix. If you want to transfer data to a PC there's a USB port. The price is reasonable, but not great (about US$500 shipped).

It did get me thinking though. If the scope had a VESA-style mount so it could bolt on to the back of a small LCD monitor, maybe they'd have something. Then again, for $500 I can pick up a pretty reasonable Rigol or Owon import on eBay with a color screen built in. And, of course, that's assuming you don't have the cash for a name brand instrument.

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