As will shortly be obvious, I have no formal training in this stuff, but fool around with TI MSP430 and Arduino projects on occasion. And it would be nice to have a scope around to help figure out how things work or what's gone wrong.
In the latest episode of KnowHow (twit.tv/KH), Fr. Robert presents an inexpensive scope kit costing $23 from BangGood:
The schematic for the DSO138 is in the Manual.
In addition, it looks like there's a more modern version currently on sale at about the same price:
The schematic for the DSO150 is in a separate link about 1/4 way down the page.
Now of course these won't be much good with microwaves, but it looks like they might be fast enough to deal with anything I might do with an Arduino, including PWM and such.
My question concerns the probe. Both of these kits provide a probe that's BNC to alligator clips. I can't tell for sure, but I doubt there's anything in there except wire. However, both circuits have two trimmer caps that in theory provide for nice square waves.
What I would prefer to use is a "real", but cheap, oscilloscope probe with the little hook-on end, or you can remove that to get just a point. And the ground lead clips on right behind the lead. Probes like this (often referred to as P6100) are available in 1x/10x form, claiming to be 100 MHz, for about $6-7 each on Ebay, and on BangGood for that matter.
What I don't know is whether there's any reason a better probe wouldn't work with these scopes. The schematics are puzzling to me because the circuits involved for the different sensitivity paths are all connected in parallel even if only one circuit output is selected, and some of those circuits connect eventually to ground. But at these relatively slow speeds, does any of this matter? If I put the probe in 10X mode, which I think I would do most of the time, isn't it just a question of whether the trimmer cap on the probe and the trimmers on the board are of sufficient range to to get those square waves to show up as square? Or are there other potential incompatibilities that I should be concerned about. Of course I can just spend the $6 and find out, but, you know, what's the fun in that. Also, if it won't work, I'd like to be able to tell Robert why.
So I would appreciate any words of wisdom that might be forthcoming.
And by the way, for the price, aren't these scopes neat? Very goosey about BangGood though.