# Is this the cheap O-Scope we've been waiting for?

#### TheLaw

Joined Sep 2, 2010
228
I kind of want an O-scope. Seeing I am into power supplies and such, I thought I might save up for a decent O-Scope. However, even eBay could not produce me a cheap quality O-Scope...so I gave up.

Today, I went on Seeedstudio, and lo and behold, the DSO Nano v2. I saw the original DSO Nano about a year ago. It looked interesting, but it was too buggy.

It's only $90 USD. The only downside I can see is that it only has a 1MHz bandwidth. http://www.seeedstudio.com/depot/dso-nano-v2-p-681.html?cPath=104_108 ------- ALSO, on January 1st, Seeed is going to be putting the DSO Quad on the market which will feature 4 channels (hence the name). 2 Analog and 2 digital. It's analog bandwidth will be roughly 30MHz. There is no pricing for it yet. If I had to predict, I'd say it would be roughly$200. But that's just a wild guess.

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Now on a more personal note....How would you determine what an appropriate bandwidth would be for an O-Scope? I would personally like one to measure output ripple in a regulated power supply. But I have a pretty good feeling 1Mhz will not be enough.

Thanks and maybe this will be good news (if you haven't seen it yet).

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#### Wendy

Joined Mar 24, 2008
21,848
I bought a used oscope from a Ham convention for $90 that goes up to 65Mhz, dual trace. You need wide bandwidth to measure switching speeds, it is an important application. Just my 2¢. Before that I was using an HP120B that had a freq response to 300Khz. It cost$10.

#### TheLaw

Joined Sep 2, 2010
228
Hmm...well I never really had much luck with eBay. I did have one miraculous event where I needed a a PC power supply of a weird formfactor and the same day this happened, someone posted an exceptionally high quality supply in that form factor....That made me happy...

But yeah I guess I'll keep looking around. Any ideas on these O-Scopes?

#### TheLaw

Joined Sep 2, 2010
228
Wide bandwidth as in like 30Mhz or 60Mhz or 200Mhz

#### Wendy

Joined Mar 24, 2008
21,848
Yep, I don't use eBay. Unless you are way out in the boondocks you can find local sources. Pawn shops tend to overprice this kind of stuff, but look for local amateur radio clubs (Ham radio). This guys tend to be fairly honest, and would rather sell something at a loss than let it go to waste. They have a saying, "Today's technology is tomorrow's junk.".

Craig's classified list is also a good venue. Think local, it is harder to cheat someone if you are there, and gas is cheaper than shipping (though not by much).

Joined Jul 7, 2009
1,577
It might be a good, basic scope in a small package. It might be a piece of junk. Personally, I couldn't tell unless I was able to try one out for a few minutes. If someone wants to send me a trial unit, I'll write a review to be posted here (I've evaluated oscilloscopes for test equipment companies, so I have some practical experience). It appears the firmware is open source, so that's a good thing, as you might be able to hack it to better suit your needs. If it works as one would expect from the specs, it sounds like a nice little tool for $90. Depending on your needs, here's a rule of thumb to evaluate a scope's bandwidth for your needs. First, the stated bandwidth is (or most experienced people will assume it to be) the 3 dB down point. This means that if you input a sine wave to the scope of 1 volt peak to peak at a "low" frequency (say, 100 times less than the bandwidth), then the scope's vertical amplifier will show the waveform to have 0.5 volts peak to peak at a waveform frequency of the rated bandwidth. The rule of thumb is to divide the bandwidth by 10 to get an idea of the useful bandwidth for a variety of signals. Remember that we often use a scope to look at switching times and to view transient events and these things, as Bill mentioned, require lots of bandwidth. Personally, I divide by 20 because I once tested a 25 MHz analog scope I bought in the 1970's with a pulse generator and that scope's performance on fast pulses and square waves led me to the divide by 20 rule (based on my judgment of how it reproduced the signal compared to scopes with higher bandwidths). BTW, that scope still works fine (it's a Philips scope) and I've used a signal generator to determine it can usefully trigger and measure the amplitude of sine waves up to 65 MHz. Thread Starter #### TheLaw Joined Sep 2, 2010 228 Yeah I don't need a super precise scope. Just something to see if my ripple is all over the place or if it is acceptable. After running through some calculations. (Thank you!), I determined that the scope should have around 25MHz bandwidth. If that "Quad" scope isn't too expensive, I might consider it...But I think I'll try to see if I can get a cheap regular o-scope. They would probably be a better deal. One thing that these scopes do offer is being able to store the data. They do make benchtop scopes with this functionality but they are$1k+ in most instances.

I live in the NYC metropolitan area so there's definitley a lot of things going on. Let's see about those ham conventions! Thanks.

#### SgtWookie

Joined Jul 17, 2007
22,201
HAM conventions are great places to pick up test equipment like that. Know your specification requirements beforehand.

You really need to be careful about online auctions; you might get a scope for cheap and wind up paying $50 or more for shipping. I bought a couple of 'scopes a few years back on an auction site; a Hitachi V-660 dual 60MHz and a Tektronix 2215 dual 60MHz. They both had known problems, so I got them for cheap - even then, shipping wound up being around$35/ea, and shipping has gone up quite a bit since then.

The really nice thing about the older 'scopes is that you can actually repair and calibrate them yourself, if you can find a service manual. The new digital scopes - forget it; they're all proprietary - and you have to pay through the nose for the software calibration routines.

#### TheLaw

Joined Sep 2, 2010
228
I see your point. Well...I guess it will come down to cost and what I am willing to sacrifice. I guess I probably don't REALLY need an O-Scope but I'd really like to know if my power supplies are destroying any sensitive RF/logic equipment I might be trying to power...

#### TheLaw

Joined Sep 2, 2010
228
It would also be helpful for many other things...but power supplies are the only things I am doing right now....

#### TheLaw

Joined Sep 2, 2010
228
I see your point. Well...I guess it will come down to cost and what I am willing to sacrifice. I guess I probably don't REALLY need an O-Scope but I'd really like to know if my power supplies are destroying any sensitive RF/logic equipment I might be trying to power...

#### marshallf3

Joined Jul 26, 2010
2,358

#### TheLaw

Joined Sep 2, 2010
228
So I should just show up to a club meeting and ask for an O-Scope?

I get the point. Thanks.

#### channelmaniac

Joined Dec 17, 2010
4
http://www.craiglook.com is a useful site - look up items by key words on any Craigslist city you want.

I picked up a nice 60MHz Tektronix dual trace LCD scope in Denver back in summer 2009 when my son and I were on one of our annual Father/Son road trips. That site helped me to search around the US and find what I was looking for.

The gentleman wanted 525 for it and I picked it up for 450 cash. It's perfect for fixing tough arcade game boards that I can't figure out with my logic probe.

RJ