EEVblog #1022 - Finding A $50 Oscilloscope On Ebay

[Gyro]

In the hope of making some sort of sense of the intention behind nctnico's post...

The lowest cost USB scope that I would suggest as a viable alternative to a $50 ebay analogue scope, for less demanding applications, would be the VDS1022.  Then you get  25MHz, 100Msps on 2 channels, with sufficient hardware and firmware in the scope itself to do proper hardware triggering (not just edge), AC/DC coupling, and actually achieve its quoted maximum sampling rates with minimal loading on the PC.

Unfortunately it fails the $50 test by nearly a factor of two:  https://www.ebay.com/sch/i.html?_from=R40&_sacat=0&_nkw=VDS1022&_sop=15

[nctnico]

I'm thinking back to when I was a teenager and had a dual channel 20MHz analog scope which could only do edge triggering. No single shot, no measurements, no screendumps.... When given the choice back then between the options in my previous post and the 20MHz analog scope I'm not so sure I would have choosen the analog scope. A DSO (even if it is a limited one or needs a PC) offers a lot of possibilities an analog oscilloscope doesn't have.
Actually someone wrote Python software for the Hantek 6022BE I linked to earlier ( https://github.com/rpcope1/Hantek6022API ). With some tinkering the possibilities are endless.

[David Hess]

I am in the US so deals and especially Tektronix deals are relatively easy to get.  My best buys have been a completely working Tektronix 2230 (100 MHz, 20MS/s, Peak Detection) on Ebay for $60 and a working Tektronix 547 (50 MHz, alternate sweep, super sharp CRT) with plug-ins and cart locally for $50.

An analog oscilloscope is suitable for a majority of applications and there is a minority of applications where an analog oscilloscope is better than a DSO.  However a novice is unlikely to be able to recognize their own requirements and evaluate a used instrument making a new but expensive DSO more desirable.

[Electro Detective]

FWIW: This advice is strictly for newbs and greybeards returning to the game, seeking to spend their initial start up pennies wisely: 

Why stuff around with a cheap DSLOw, when the real action is with a cheap fully WORKING classic analogue oscilloscope?

Quickly switch and dial up waveforms, instead of ploughing through menus with quirky toy knobs, waiting on software bugs updates that may never come or they bug fix one issue and create ten more,
contemplating noisy fan replacements,
praying it still works past the warranty period because you know deep down it's a   'not worth fixing'   throwaway job once it dies 

Get a cro, and get on with it! 

$120 > $250 spent on a good fully working scope won't send you to the poor house (in Australia)


In most cases (99%) a $50 cro will get you OTHER PEOPLES PROBLEMS and lost bench real estate
(or shed space waiting to toss it, or have another futile go at fixing the sucker, if you can allocate more time to waste... )

[buck converter]

ATTENTIONS TEENS: You are special when it comes to getting these analog scopes. This past summer I went to a generic STEM camp at a local university. Walk past a dumpster loaded with scopes. Now I already had a CRO , but I knew I could sell these if I could get my hands on them, and raise money for my robotics club. I only walked out with one, a working Tek 2235. For free . What I am trying to say is that if your a teen, ask local universities with electrical engineering programs if they don't need them. It doesn't cost any money to ask, and could build connections, especially if you are already attending a STEM camp .

[eugenenine]

Always sad to see stuff like that in a dumpster.
Anyone ever played with one of these http://www.gabotronics.com/development-boards/xmega-xprotolab.htm

[Smokey]

...An analog oscilloscope is suitable for a majority of applications and there is a minority of applications where an analog oscilloscope is better than a DSO. 

I would like to hear your list, even a minority list, where an analog scope is better than a DSO.  Not just equivalent, or sufficient, but better.

Also saying an analog scope is suitable for a MAJORITY of applications is not very truthful.  The majority of scope application these days are NOT looking at repetitive signals, which makes an analog scope not suitable (unless you suggest everyone also gets one of those Tek camera adapters to take triggered pictures).  The world of embedded systems requires a DSO (or a lot of guessing).

[boffin]

There's going to be plenty of arguments

"I can't find one for $50"
"A digital USB scope is useless"
"Dave does these videos for the money"

Well, there might be some truth to the first two, I'm pretty sure Dave isn't getting rich from his youtube channel.  $40k last year (checkout eevblog# 959) - that's peanuts when you compare his expenses.

However, keep looking. 
I bought a used Analog Discovery for C$100; and it's really useful. REALLY.
I bought a broken Philips 3216 (35MHz) for C$10, and replaced a 50c trimmer to get it working.  I did spend $15 on some de-oxit.  Still, C$25 total

They both have their place.

There's a Tek 2213 (60Mhz) on the local Craigslist right now for C$200 in what looks like great shape. It's been there a while, so I'll bet you could get it for C$150. Sure it's not $50, but it's still 1/3 the price of a new Rigol; and probably way more scope than most beginners need.

People take things way too literally. I'm sure you can find a scope for $50, it just might take some time - Dave is trying to make a point. 
However for double that (or a tiny bit more), you could have a [nice] scope by the end of the day if you really wanted one.

[nctnico]

An analog oscilloscope is suitable for a majority of applications and there is a minority of applications where an analog oscilloscope is better than a DSO.  However a novice is unlikely to be able to recognize their own requirements and evaluate a used instrument making a new but expensive DSO more desirable.

That is a way too generic statement. What I hated about my 20MHz analog scope was that it absolutely sucked at showing slow waveforms and I needed to count divisions + do math to get amplitude, time, frequency, etc.

[David Hess]

...An analog oscilloscope is suitable for a majority of applications and there is a minority of applications where an analog oscilloscope is better than a DSO.

I would like to hear your list, even a minority list, where an analog scope is better than a DSO.  Not just equivalent, or sufficient, but better.

Measuring RMS noise is one of them that I keep coming up against.  In theory any DSO with RMS measurement capability should be able to do this (it is trivial in the digital domain) however DSOs which make measurements on the processed display record which are apparently a majority now cannot.  And unfortunately no DSO yet duplicates the response of an analog CRT so they cannot do tangential RMS measurement either as an alternative.

Finding snivets is another problem that I have run up against with DSOs.  Again, most should be able to do this however the processing used for index grading the display tends to cover them up when it should not.  This is an aspect of DSO displays looking noisier than analog displays whether they truly are noisier or not.

The majority of scope application these days are NOT looking at repetitive signals, ...

We will have to disagree on this point and especially so since non-storage oscilloscopes can still be used in many cases on non-repetitive signals.

That is a way too generic statement. What I hated about my 20MHz analog scope was that it absolutely sucked at showing slow waveforms and I needed to count divisions + do math to get amplitude, time, frequency, etc.

Obviously a storage oscilloscope is indispensable at low repetition rates but of all of the applications, how many require this?

[Fungus]

Measuring RMS noise is one of them that I keep coming up against.  In theory any DSO with RMS measurement capability should be able to do this (it is trivial in the digital domain) however DSOs which make measurements on the processed display record which are apparently a majority now cannot. 

Maybe you underestimate the processing power needed for that (and if they did a slow-updating display you'd just complain about that instead).

You can:
a) Download the memory to a PC for processing with nothing more than an Ethernet cable and a free program.
b) Use a TRMS multimeter, they cost about $15 these days and are the correct tool for the job. DSOs are for looking at wiggly lines and getting approximate measurements.

[Smokey]

...
Finding snivets is another problem that I have run up against with DSOs.  Again, most should be able to do this however the processing used for index grading the display tends to cover them up when it should not.  This is an aspect of DSO displays looking noisier than analog displays whether they truly are noisier or not.
...

Never heard of a Snivet before.   I had to look this up. 
http://amfone.net/Amforum/index.php?topic=35557.0

"One of the phenomena that has appeared in the image reproduced in the television receiver is known as the snivet. Snivets are thin parallel vertical lines which may appear at one or more positions of the reproduced image. lt has been suggested that the production of such thin vertical lines is due to Barlthausen oscillations developed in the horizontal output tube. Barlrhausen oscillations may be produced in a tube when a positive electrode is arranged between two more negative electrodes. The electrons present in the tube are repelled by the more negative electrodes back toward the positive electrode. The oscillations caused by the alternate attraction and repelling of electrons occurs in a frequency range determined by the dimensions and spacing of the electrodes and the potentials applied thereto. Such oscillations may produce radio frequency radiation in the video carrier frequency range of the television receiver. T is radiation will then be detected and pass through such receiver in substantially the same manner as the video signal. The received radiation is then reproduced on the cathode ray screen in the form of the above-referred to thin vertical lines. "

So it sounds like one of your examples for when ancient analog scopes is better is essentially when working on other ancient analog scope CRTs?  Can you even buy a CRT TV now?  Can't say I can think of a lot of other CRT uses these days. 

[kalel]

So it sounds like one of your examples for when ancient analog scopes is better is essentially when working on other ancient analog scope CRTs?  Can you even buy a CRT TV now?  Can't say I can think of a lot of other CRT uses these days.

You probably can, I think I saw some smaller, low end units being sold in some shop (don't quote me on that). As for uses, maybe game emulators? If some were originally intended for a CRT, and you wanted more faithful reproduction, I doubt that the filters that some emulation tools have really reproduce CRT's faithfully on an LCD. That said, it is much easier to look at a quality LCD screen, even if older games don't always look that great due to their resolution.
 

[b_force]

An analog oscilloscope is suitable for a majority of applications and there is a minority of applications where an analog oscilloscope is better than a DSO.  However a novice is unlikely to be able to recognize their own requirements and evaluate a used instrument making a new but expensive DSO more desirable.

That is a way too generic statement. What I hated about my 20MHz analog scope was that it absolutely sucked at showing slow waveforms and I needed to count divisions + do math to get amplitude, time, frequency, etc.

I guess that's being considered as minor things maybe?
Yes, I also like digital scopes much better for these reasons.
But on the other side, back in the days we even didn't have that luxury?

So in a sense I totally agree with that statement a lot.
I see to many people bragging about their fancy equipment, but most of the time they don't even using it.
Or even worse, don't even take people serious anymore with cheaper equipment.
The fact that someone is on a tight budget, doesn't mean that they don't know what they are doing.
(in fact, it's mostly the opposite)

Ones again, people go into details. I think everyone can see/read that digital scopes have a lot more luxury.
But, hey, if you just wanna develop stuff and you're on a tight budget, there are options available
In fact, in most cases you only wanna see if signals are coming through, so you don't even need math functions.

Only thing I would like to add to the video, is that it's not entirely fair.
The cheap scopes are all based in the US or Asia. So that means you have to pay a lot of import tax and shipping.
Second hand market in EU is actually pretty bad to be honest.
People ask ridiculous prices or trash it. There is nothing in between.

[nctnico]

An analog oscilloscope is suitable for a majority of applications and there is a minority of applications where an analog oscilloscope is better than a DSO.  However a novice is unlikely to be able to recognize their own requirements and evaluate a used instrument making a new but expensive DSO more desirable.

That is a way too generic statement. What I hated about my 20MHz analog scope was that it absolutely sucked at showing slow waveforms and I needed to count divisions + do math to get amplitude, time, frequency, etc.

I guess that's being considered as minor things maybe?
Yes, I also like digital scopes much better for these reasons.
But on the other side, back in the days we even didn't have that luxury?

So in a sense I totally agree with that statement a lot.
I see to many people bragging about their fancy equipment, but most of the time they don't even using it.

Why would you have to use fancy features every time? What is important is that if you need it, it is there and it will make life easier. For example: I have a very nice Tektronix logic analyser but it is only on for a couple of hours per year. So I don't need it a lot but it is darn handy to have it available and be able to use it when necessary.

[b_force]

An analog oscilloscope is suitable for a majority of applications and there is a minority of applications where an analog oscilloscope is better than a DSO.  However a novice is unlikely to be able to recognize their own requirements and evaluate a used instrument making a new but expensive DSO more desirable.

That is a way too generic statement. What I hated about my 20MHz analog scope was that it absolutely sucked at showing slow waveforms and I needed to count divisions + do math to get amplitude, time, frequency, etc.

I guess that's being considered as minor things maybe?
Yes, I also like digital scopes much better for these reasons.
But on the other side, back in the days we even didn't have that luxury?

So in a sense I totally agree with that statement a lot.
I see to many people bragging about their fancy equipment, but most of the time they don't even using it.

Why would you have to use fancy features every time? What is important is that if you need it, it is there and it will make life easier. For example: I have a very nice Tektronix logic analyser but it is only on for a couple of hours per year. So I don't need it a lot but it is darn handy to have it available and be able to use it when necessary.

I am not saying there is anything wrong with it?
I totally agree with you, but I am just saying it's pure luxury.
So if you go back to the basics, you don't really need it.
Which is good to know for people on a tight budget for example.

[Fungus]

What I hated about my 20MHz analog scope was that it absolutely sucked at showing slow waveforms and I needed to count divisions + do math to get amplitude, time, frequency, etc.

I don't think anybody would deny that CROs are better looking and DSOs or more fun to use. I love the green traces, they look awesome compared to my Rigol's pixels.

But ... they do show a lot less information once you go outside their optimal settings and being able to record the waveform and zoom in on a DSO is invaluable.

CROs are perfect for looking at repetitive signals but that's not really the world we live in any more. The modern world is full of microcontrollers and digital signals and in that world the DSO is king

[nctnico]

An analog oscilloscope is suitable for a majority of applications and there is a minority of applications where an analog oscilloscope is better than a DSO.  However a novice is unlikely to be able to recognize their own requirements and evaluate a used instrument making a new but expensive DSO more desirable.

That is a way too generic statement. What I hated about my 20MHz analog scope was that it absolutely sucked at showing slow waveforms and I needed to count divisions + do math to get amplitude, time, frequency, etc.

I guess that's being considered as minor things maybe?
Yes, I also like digital scopes much better for these reasons.
But on the other side, back in the days we even didn't have that luxury?

So in a sense I totally agree with that statement a lot.
I see to many people bragging about their fancy equipment, but most of the time they don't even using it.

Why would you have to use fancy features every time? What is important is that if you need it, it is there and it will make life easier. For example: I have a very nice Tektronix logic analyser but it is only on for a couple of hours per year. So I don't need it a lot but it is darn handy to have it available and be able to use it when necessary.

I am not saying there is anything wrong with it?
I totally agree with you, but I am just saying it's pure luxury.
So if you go back to the basics, you don't really need it.
Which is good to know for people on a tight budget for example.

The thing is: nowadays you don't have to compromise. There are tons of cheap DSOs out there. I only linked to the first two ones I found on Aliexpress.

[Fungus]

But, hey, if you just wanna develop stuff and you're on a tight budget, there are options available
In fact, in most cases you only wanna see if signals are coming through, so you don't even need math functions.

I don't think I've ever used a math function, I do an awful lot of capturing/zooming though.

Only thing I would like to add to the video, is that it's not entirely fair.
The cheap scopes are all based in the US or Asia. So that means you have to pay a lot of import tax and shipping.
Second hand market in EU is actually pretty bad to be honest.
People ask ridiculous prices or trash it. There is nothing in between.

Yep. Buying in Europe is a completely different story. I think Germany is maybe the best place to look but even then there's bugger all compared to the USA.

[Gyro]

The thing is: nowadays you don't have to compromise. There are tons of cheap DSOs out there. I only linked to the first two ones I found on Aliexpress.

You just need to make sure that you don't link products that drop below the 'frustration threshold' - that way lies misery and buyer's remorse. 

[b_force]

I still found a "$50" analog Philips or so, a whole lot better than these cheapo USB thingies.
Like I said, I think 50 bucks is a little bit to positive, but still, you can't find a decent digital scope between 50-100 bucks.
But maybe that's just purely subjective.

It's frustrating though, these USB scope things do have heaps of potential.
They just screw it up in the software, which is to unfortunate.

[Gyro]

I still set the lower limit of  'acceptability' (of USB models) at the VDS1022.  Below that, the Hantek, Sainsmart etc. are horribly compromised, either in H/W, S/W or meeting their specified performance.

[b_force]

I still set the lower limit of  'acceptability' (of USB models) at the VDS1022.  Below that, the Hantek, Sainsmart etc. are horribly compromised, either in H/W, S/W or meeting their specified performance.

Agree, although the isolated variation (or USB isolator) would be very wise.

My personal main issue is just the interface.
I think it just doesn't really work with a mouse when measuring live stuff.
I like to use knobs, works much quicker and more intuitive
You could probably get away with a DAW controller or so, but than you can better buy a better scope.
Or you need to build something yourself of course  

[David Hess]

Measuring RMS noise is one of them that I keep coming up against.  In theory any DSO with RMS measurement capability should be able to do this (it is trivial in the digital domain) however DSOs which make measurements on the processed display record which are apparently a majority now cannot.

Maybe you underestimate the processing power needed for that (and if they did a slow-updating display you'd just complain about that instead).

You are joking, right?  I hope you are joking.

You can:
a) Download the memory to a PC for processing with nothing more than an Ethernet cable and a free program.

I have done it this way before.  At one time I even had my HP calculator programmed to do it with a sampling voltmeter but that was at low frequencies.

b) Use a TRMS multimeter, they cost about $15 these days and are the correct tool for the job. DSOs are for looking at wiggly lines and getting approximate measurements.

Multimeters do not have nearly the bandwidth of even a slow oscilloscope.  The bandwidth requirements are usually modest but multimeters are not even close.

...
Finding snivets is another problem that I have run up against with DSOs.  Again, most should be able to do this however the processing used for index grading the display tends to cover them up when it should not.  This is an aspect of DSO displays looking noisier than analog displays whether they truly are noisier or not.
...

...

So it sounds like one of your examples for when ancient analog scopes is better is essentially when working on other ancient analog scope CRTs?  Can you even buy a CRT TV now?  Can't say I can think of a lot of other CRT uses these days.

A snivet is a negative resistance parasitic oscillation.  It most commonly shows up in emitter/source followers.  The name originated from the negative resistance oscillation in a sweep tetrode at low anode voltage which showed up as described by your link as a visual disturbance on television CRTs.

[ez24]

The reality is buying a 30 or 40 year old oscilloscope is probabily a waste of time and money. 

Was for me - twice.