The DSO has been high on my want list for some time now.. But that said, I made it through several Commodore machines & drives, the CRT display on the Osborne Vixen, the Altair rebuild, several Macs and on, with what I do have on-hand. Lacking a DSO didn't prevent me from getting through that stuff, but I'm sure it slowed me down more than once. On Mon, Aug 17, 2015 at 3:16 PM, geneb <geneb at deltasoft.com> wrote:

Hey Dave & All, Could you give a little quick kick-start guide to bit depth & sampling rate on DSOs? It's always kind of stumped me, not that I've ever read deeply into it.. but how is it that you can get any kind of (vertical, right?) resolution out of 8 or even 12-bit samples? Example line of thought - 8 bit sample = 256 possible vertical positions. Even if the screen is low-end (640 x 480) that's almost 2X more height in pixels than samples in an 8-bit sample. So each increment is like 2 pixels tall and seems like it would be awfully blocky and imprecise. Things would seem to get even worse if you try to do maths functions.. I must be viewing this quite wrong? On Mon, Aug 17, 2015 at 3:55 PM, Dave G4UGM <dave.g4ugm at gmail.com> wrote:

It depends on the screen resolution. My Tek 602, a rather early (and very large/heavy) DSO, does just fine with 8 bits because the screen is fairly small. Compared to the screen resolution of a typical analog oscilloscope screen, 8 bits is a pretty good choice. You can occasionally find DSOs with higher resolution, but there?s a substantial penalty in sample rate. Nyquist rule: you need 2x the sample rate of the highest signal frequency. Or more accurately, the bandwidth. That?s the same thing if you start at 0 Hz, but if you?re sampling a piece of spectrum, you only need 2x the bandwidth of the band in question, not 2x the frequency of the upper edge. Note also that you have to consider filter skirts, so you need 2x the frequency at which your input filter has ?high enough? attenuation. To pick an extreme example, the current record holder DSO has 100 GHz (!) bandwidth and 240 Gs/s sampling rate. You would not display them as 2 pixels tall. Typically the display machinery will interconnect the sample points by lines, and the result usually looks pretty convincingly like an analog scope display (unless you crank the zoom way up). As for math, that depends. If your math involves filtering, the effective bit count goes up (the ?processing gain? DSP people speak of). paul

@ Jay, Ha, yeah.. I've seen a number of his vids.. Don't mean to offend, but he comes off a bit squirrely (hyper) for me. Yet another freaking Aussie nutcase, lol - but he does seem to get some good info across, in between the audible glamour. On Mon, Aug 17, 2015 at 9:54 PM, Jay Jaeger <cube1 at charter.net> wrote:

I used to watch Dave but his ego got to be a bit much for me ... I now prefer "mikesslectricstuff" and "w2aew" on YT when I'm looking for some inspiration in the form of a video. Best, Sean On Tue, Aug 18, 2015 at 9:12 AM, Jay Jaeger <cube1 at charter.net> wrote:

The videos below are from 2009 so are now 6 years old, so about the same age as windows/7. I don't know of any modern USB scope that does equivalent time sampling. Memory Depth isn't so important as USB2 means you can shift the data pretty quickly into the PC. I also note he says proudly he doesn?t have a PC in is lab. I have several and they are really useful for many things. In 2009 I probably didn't, but these days they server as audio signal generators, audio frequency counters, and Audio oscilloscopes. with a DVB memory stick inserted they provide low cost, reasonable quality spectrum analysis. As for displaying the scope output how many scopes have a 14" screen. Those with a reasonable cost all have smaller screens where 8-bit sampling is probably OK. Note the Rigol he proudly trumpets has a 5.7" display. Yuk!. I also have recording 3.5 digit DVM with a USB interface. Good for recording data over short periods.... As he says for us with higher speed devices you probably want a 20Mhz displayable bandwidth, so I would say 80mhz sampling Minimum, he says 200Mhz, but for older vintage stuff you are seldom going to be going that fast. I own a DSO5200 as mentioned in the videos and its great, but the only time I have used its full abilities was to test a 0-30Mhz Direct Digital Synthesis frequency generator I built. I actually recently went and bought a 6022 as well. At the price I just don't worry about it, I throw it in the laptop bag and away I go. Well 12-bit is, imho a total waste of money for Computer Restoration or really most work. That?s equivalent to about 250 microvolts on a 0v to 1volt signal. I could see an argument for 10-bit which is about 1 millivolt on a 0v to 1volt signal, but that?s the most you can display on a 1168x1024 screen and even then you won't fit it all in as you will have some borders. (Double those figures for symmetric +/-1volt audio) As someone else said 8-bits resolution is 4 pixels on a modern screen, but this laptop so that?s how far the signal jumps. If you go for analog scopes then the screen size will be significantly smaller so you won't get anywhere near that resolution, and even on a very good scope I am pretty sure the spot size will be greater than 1 pixel. This laptop, which is typically what I use the USB scopes with is actually only 900 pixels vertically so about three pixels per step. Lastly I also own 2 analogue scopes, both old, a Tektronix 453 and a "no name" TV engineer scope that our local college sold when it stopped teaching TV repair. There are times when both of these are useful, but if I had to choose then I would take either of the USB scopes any day. In short I guess it is all down to what is called "opportunity cost". Spend $60 on a scope and the fastest CPU you can debug will be an 8Mhz z80 or 8086. For $200 you are in the higher speed 68030 arena... Dave G4UGM