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Oscilloscope for testing DIY modules
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Author Oscilloscope for testing DIY modules
southafrica
Hi everyone

Seeing as I'll be building and designing all of my own modules for my synthesizer, I figured that having an oscilloscope would help debug any problems, speed up development of my modules and make tweaking them easier. I'm sure most of the high end oscilloscopes are overkill for modular synthesis DIY so what features should I be looking for? Do I really need to fork out $400+ for a new oscilloscope or are there cheaper alternatives that do the job perfectly fine?

Most of my modules will be running off of 9V, maybe a few off of 5V (not sure how important that is when choosing an oscilloscope that's why I'm asking, this is all very new to me).

Any recommendations/advice/feedback is greatly appreciated, thanks.
Altitude909
For basic stuff, I ditched my big analog one for one of these: http://www.amazon.com/Seeedstudio-DSO-Nano-oscilloscope-V2/dp/B004DE31 U0
Electronic Battle
Hello

My suggestion is to save a bit more and get something with wider bandwidth and better y axis sensitivity too if possible. A single channel is a bit of a pain. How well does the scope trigger? The y amps might have 1MHz of bandwidth but will it trigger reliably at 1MHz? What about decent scopes which will trigger well beyond their y amplitude bandwidth - you can still resolve waveforms with good relative (but poor absolute) accuracy - how wil this nano compare?

It's a pretty neat gadget and may be of some limited use but, if you plan to do anything other than low frequency analogue synthesiser stuff (i.e. audio frequencies) then you'll need something better. What about trying to measure noise on a switched-mode PSU? Or digital stuff?


Seeedstudio DSO nano specs, [and my comments following]

Specifications:
Display Full Color 2.8" TFT LCD 65K 320×240 [physically, though, a pretty small screen and not easy for seeing waveform artefacts]

Max sample rate 1Msps 12Bits [OK for vertical resolution, but 1megasample/s is very slow]

Analog bandwidth 0 - 1MHz [Nyquist's limit may predict that you have to sample twice per cycle but that won't resolve anything other than an interpreted sinewave response. Really, you need to be oversampling 10x - in other words, this Nano scope will give useful information upto 100kHz only]

Vertical sensitivity 10mV/Div~10V/Div (with ×1 probe) [OK I suppose] but you might consider that a 1M impedance is a bt low and you might want to be seing noise at less than a millivolt. Remembe the tiny screen is difficult to see, so a division of noise wil be difficult to see. More sensitivity needed, I feel]

0.5V/Div~100V/Div (with ×10 probe) [hopeless lower sensitivity - see above]

Coupling DCs [no AC available?]

I would recommend getting something that can measure 2x the minimum frequency you want to look at, which then implies a sampling rate of 10x greater than that value i.e. 100x the highest frequency.

A 100kHz signal of interest would need a 2Msample/s scope;
A 1MHz signal of interest would want to be captured by a 40Msample/s scope.

Look at the specs of a few full-spec scopes e.g. a cheapish Tektronix TDS - 1 gigasample/second for a 60MHz analogue bandwidth BUT it will reliably trigger past 150MHz and display waveforms well enough to do peaking up of filters etc.

So ...will you only ever use your scope for analogue synthesiser circuits with no faster clocks tha 100kHz? I bought a secondhand Tektronix TDS210 digital storage scope which now go for about $350: see eBay item no. 180736638549

There's a load of cheapish (but possibly quite good) Chinese scopes which can have their firmware upgraded - never used one but they seem promising. I forget the brand names right now but will edit and post if I remember them.

Oh yes: Rigol is one of the brands.

http://hackaday.com/2010/03/31/update-50mhz-to-100mhz-scope-conversion  /

Also Tenma (may be the same company or at least using a similar main board and display)

GW Instek is the final of the three I was thinking of.
Altitude909
Works fine for basic analog stuff. I use it to tune and test x0xb0xes. Triggering has never been a problem for me. Obviously I'm not going to be using it to analyze gigabit ethernet connections but he fact that it fits into the front pocket of your shirt and is battery powered makes it super convenient to use and really does cover most duties I would need. They also make a quad now for a $100 more. The V2 can be found on ebay for as low as $60
Joe.
Owon 5022.

You can get them for about $300 inc shipping, from eBay.
Electronic Battle
Altitude909 makes a good point in that he's actually used it in anger and is happy with it.

So, perhaps we should consider the comments I made in a different
light - namely, get the nano and see how you get on with it, and then "upgrade" if you find it necessary after a few years. The nano is cheap enough to be "disposable" in that you could sell it second-hand.

Another thought that occurred to me; you don't *have* to have a digital storage 'scope. A good quality second-hand analogue 'scope, combined with a digital camera (on your phone maybe) for those times when you need to record data, would suit very nicely. In some ways a cheap digital isn't as good as a quality analogue; admittedly you lose some of the convenience but then again, it's still easy to measure waveforms from the graticule on an analogue scope without all of the ease-of-use cursors and automation. With digital scopes you sometimes need to know what the signal should look like to be able to interpret what the display is showing you, especially on fast edges or on short-duration events (glitches or runt pulses) whereas an analogue scope s more reliably showing you what there actually is (but then again you can't always see fast events on an analogue scope either).

A decent second-hand analogue 'scope could be a Tektronix 2225 or similar (eBay 310351268698) - Philips also do some nice ones.

If I was deciding, with my money (in short supply though that money is), I'd still save up for a fully-fledged 'scope myself though.
southafrica
Thanks guys for all that information, especially Electronic Battle (again) for that huge reply. I appreciate all the time you put into it. I'm going to research some of the mentioned scopes a bit more before I spend a couple hundred bucks. I'm not 100% sold on that nano to be honest. I'm leaning more towards an analog scope, I don't have very complex needs so half the features on the Rigol or the Owon mentioned above would probably go unused. But I'm not knocking them completely yet, like I said, I'll research it a bit more and sleep on it before I make a choice. Thanks again for all the information guys.
Christopher Winkels
Someone on this site could make a good buck by buying up cheap old analogue scopes, cleaning and reconditioning them (if necessary) and selling them bundled with all necessary cables for 1/8" or 1/4" plug-and-play use.

Just sayin'.
clack
I have an analogue scope that can go upto quad channel but I find when designing I never really need more than 1. There are companies that sell them second hand and serviced mine was about £150, 100Mhz and has a cool glowing grid overlay.

The problem with an analogue scope is they have to be really deep, mine almost fills my whole desk depth wise! For building and calibrating you really don't need anything too fancy, an analogue synthesizer is not a high spec electronic instrument, as soon as this one's tube pops im going to get a handheld one!
maskull
What exactly are you going to be using the scope to look at? Audio range frequencies only, or are you going to be working with micro controllers?

You can use any scope for audio frequencies, but if you move into digital signaling, you will need something with more bandwidth.

Analog scopes aren't bad as long as you have the space and are able to repair/calibrate them as needed.

I have a Rigol DS1052E that I hacked the firmware to 100MHz and am very happy with it for my at-home DIY stuff.
sduck
You really don't need much if you're just doing analog synth stuff. Two channels is very nice to have, but besides that almost anything will work. I picked up a used Heath 25mHz dual channel scope on ebay for 21$, added some probes for 14$ more, and it works great for all my needs.
EATyourGUITAR
LoFi Junglist wrote:
Owon 5022.

You can get them for about $300 inc shipping, from eBay.

thanks for the tip! I also found the picoscope USB 2 channel with arbitrary waveform generator for less than the velleman USB 2 ch scope. its also smaller w00t
Bergfotron
You need something that can show at least 10 MHz, because one of the most common problems is self-oscillation. Modern op-amps like the TL072 can easily self-oscillate in the megahertz range. You'll want to catch that.
Pfurmel
LoFi Junglist wrote:
Owon 5022.

You can get them for about $300 inc shipping, from eBay.


Anyone have any experience with these, they look like good value on paper at least? I read a bit online and there was some problems with earlier OS systems.
Joe.
I can't think of the others off the top of my head, but I've spotted a couple of other wigglers using these from Pictures of thier studios/workshops. I'm perfectly happy with mine, haven't had any problems.

My trade school upgraded one of the labs to Rigols in the last year of my apprentaceship (so a few years ago, early model), and they had a problem where they would randomly freeze up, and you would have to switch them off for a second to restart them. I don't know what the quality of them is now, but that's the main reason i went for an Owon when my CRO died.
ringstone
southafrica wrote:

Most of my modules will be running off of 9V, maybe a few off of 5V (not sure how important that is when choosing an oscilloscope that's why I'm asking, this is all very new to me).


9V? That's an odd choice... most modules/synth designs run off +/- 12 or 15V...

Blair
southafrica
ringstone wrote:
southafrica wrote:

Most of my modules will be running off of 9V, maybe a few off of 5V (not sure how important that is when choosing an oscilloscope that's why I'm asking, this is all very new to me).


9V? That's an odd choice... most modules/synth designs run off +/- 12 or 15V...

Blair


That might and probably will change, the circuits I'm looking at right now are using 9V. They're just simple intro circuits, nothing too complex yet. Why do most synth modules use 12V/15V by the way? Is it so that you can get a wider range of frequencies on things like VCOs?
Neutron7
I have a Rigol DS1052E, which i would not really recommend if you are working on LFO and other low frequency stuff.

For instance in XY mode with low frequencies, you see the trace less than 20% of the time.

I am not quite sure why it does that, but asked for recommendation on eevblog.
southafrica
Neutron7 wrote:
I have a Rigol DS1052E, which i would not really recommend if you are working on LFO and other low frequency stuff.

For instance in XY mode with low frequencies, you see the trace less than 20% of the time.

I am not quite sure why it does that, but asked for recommendation on eevblog.


Thanks for sharing that. Another question I have is what is the lowest frequency you really need your scope to trace when it comes to modular synthesis? What's the lowest rate offered by most LFOs generally?
Electronic Battle
Don't forget you might want to monitor

envelope generators ...
DC voltages ...
LFOs down to a few tens of millihertz in some cases...

You might want to see high frequency oscillations (tens of MHz) as mentioned earlier in the thread, due to op-amps or logic circuits ringing when driving lines or badly laid out, so really the top end is what you need to define.
Electronic Battle
Just found a new source of scopes (UK, but these models are likely to be available elsewhere I would think)

http://labtronix.co.uk/drupal/shop/oscilloscope.htm

This model looks a good starting point: it would do very nicely as a general purpose scope for most things.

http://www.labtronix.co.uk/drupal/shop/oscilloscope/utd2025c.htm
tailwagger
Rigol DS1052E.........$329 new, has hacks to increase to 100MHz. Even cheaper used on fleabay.

Always check the local craigslist for oscilloscopes.
Dave Kendall
If you have the space on the workbench, an analogue scope is a nice tool to have.
Two channels is good for comparing inputs with outputs, and 20mHz and upwards is good. If you go that route, it should cost between US$100 - 300 for a new bargain or second hand.
I scored a Tenma 20mHz dual-channel for 100UKP (new!) a few years back, and it's done a great job.

Good luck!

cheers,
Dave
LektroiD
I didn't spend too much in this area, I have an old 40MHz analogue one that I got from ebay for about £40. All I need it for is checking waveforms of oscillators etc...
idealer
Gabotronics protolab is a interesting very small scope that fits on a prototype board
I just got mine the other day and it seems very nice to use togeter with a android tablet or cellphone. . The pc software seems very buggy and betaish. . And it is cheep too
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