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USB oscilloscopes - are they any good?

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Robin Graham11/08/2017 22:37:45
329 forum posts
31 photos

I recently bought my first (I doubt it will be the last!) Arduino and I'm getting interested in this stuff. I'd quite like a 'scope so I could better see what's going on. I'[m thinking that I don't need enormous bandwidth (20MHz?) and I'm wondering if one of the many USB units out there around the £50 mark would work for this kind of thing. If anyone out there has experiences/recommendations, I'd be glad to hear them.

The cheapest stand-alone 'scope I've come across so far in my researches is a Hantek 100Mhz at around £200, which is doable, but maybe overkill for what I need?

Personally I think that every well-equipped modern household should have at least one oscilloscope, but I have so far failed to make my wife see what has now become to me a self-evident truth.

Rob

Paul Lousick11/08/2017 23:12:03
737 forum posts
386 photos

Hi Rob,

Why not for your Second project, build an Arduino oscilloscope ? Do a Google search. Lots of information about scope projects on the web. Kill 2 birds with one stone as they say !

Paul.

Shed Happens11/08/2017 23:17:06
21 forum posts
1 photos

Hi,

I agree, no house should be without an oscilloscope , oh and a logic analyser!

I have USB versions of both, and you can now get them as a combined unit. A few things to look out for ..... the ADC resolution or sometimes called the vertical resolution - the cheaper ones are only 8bit. The sample rate and the sample depth , depth is the amount of memory and will determine the real number of samples you can capture at a selected sample rate.

At the end of the day like most things it will depend on what you end up wanting to do with it. No doubt a basic unit will give you significant insight but if you plan on doing more involved electronics then you might end up wanting a better spec.

FYI I have a PICO scope and a ZEROPLUS logic analyzer.

John

duncan webster12/08/2017 00:12:40
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1265 forum posts
14 photos

If you've got a computer with a parallel port I can let you have an old picoscope for a small donation to the Sally Ann

XD 35112/08/2017 00:22:48
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656 forum posts
26 photos

A local electronics magazine i read did a reveiw on an scope kit - i believe it was from banggood but may have been amazon can't recall . It came with the surface mount components already soldered but you have to solder the through hole components on and fit it into the acrylic case that is supplied .

They gave it a good work over and were impressed with its performance for under $50 au .

I use a little hand held vellman unit and it does what i need but it is a pretty a limited unit .

Usual disclaime applies .

Mike Clarke12/08/2017 05:28:35
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73 forum posts
5 photos
I'm a huge fan of Picoscopes. The software makes it for me.......some great serial decoders for example. The software is also continually upgraded.

If you keep an eye on eBay they sometimes do some really good deals via their official store.

Mike
Russell Eberhardt12/08/2017 08:08:23
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2077 forum posts
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For working with the Arduino it's worth spending a bit more and getting a Bitscope. It acts as a logic analyser at the same time as an analogue oscilloscope. The software is much better than that with the Chinese ones.

Russell.

John Haine12/08/2017 08:12:51
1569 forum posts
92 photos

After thinking about this I went for the Hantek since it has its own screen and lots of useful features. Seems to do what I want, compares well even against the professional scopes I used to use many years ago at work. But paid only £175 for it.

HughE12/08/2017 08:16:53
70 forum posts

I purchased one from Bangood for about 12 GBP . As XD351 says it comes part assembled. If you go this route the fiddly bit is to ensure the pin headers are aligned correctly before soldering. I fitted mine to different case to include a battery. There is useful info on various forums about improving performance. I have been pleased with mine as its very portable. I do have an ex us navy Tektronic which is bulky which I use most of the time. Space may dictate that I get rid of it an go for a Pico.

Hugh

Mike Poole12/08/2017 08:21:20
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996 forum posts
30 photos

Pico are probably the leader in USB scopes etc. But as usual expect to pay a premium for the best.

Mike

Joseph Noci 112/08/2017 08:32:12
194 forum posts
496 photos

Hello Robin,

Forgive the dissertation...

As a radio ham, and Electronic engineer, I can tell you that the two MOST used instruments in my shack are the multimeter ( get the best you can afford!) and the oscilloscope. I have two 'scopes, both 'modern' digital, one HP and and my latest one from Keysight who where Agilent who were HP...

For me the most important feature of a DIGITAL scope is its sample rate and memory depth. My Keysight scope has a 5GHz sample rate, which is probably a huge overkill for your application, but in essence you need a sample rate that is AT LEAST twice the measured frequency. Even this can lead your up the garden path if you are not careful. There is something called the Nyquist Sample rate theorem, which says

'the minimum rate at which a signal can be sampled without introducing errors, which is twice the highest frequency present in the signal'

Sampling slower, and even at twice the rate, leads to what is known as aliasing - basically the observed signal can be sampled to appear as a sub-harmonic of the actual frequency - showing something completely different to what is actually true!

If you believe the signals you are interested in would never exceed 20MHz, then a 100MHz scope should be sought...

If it is an analogue scope then the Nyquist issue does not apply, but the speed of the input amplifiers play a big role, and so, again, a 100MHz scope needs be for your 20MHz application..

Of course, analogue scope do not have storage, so capturing short pulses, and glitches is not possible. Except for some scopes with storage Phosphor screen displays - stay away from those!

I mentioned glitches - These are the bane of digital electronics! For example, your Arduinio works fine, driving the X table autofeed of you bench mill, TILL you switch on the spindle motor. Then the Arduino goes haywire..So it seems to be a spike somehow getting into the gubbins...This is generally a very short 'glitch' or voltage spike that upsets the works, and these glitches can be from a few nanoseconds period, to seconds..the latter easily captured on a 100MHz digital scope, the former, no chance...

Some digital scopes of low sample rates have special glitch capture features - they can 'see' and trigger on a glitch, and then will artificially stretch it for display purposes. Glitch capture/observation is in my opinion essential if you fiddle in the digital domain...

Then, sample memory depth. This means the amount of data that can be captured and displayed on the screen. If observing a fast pulse train, and you need to analyse the data within the train ( say for example, a USB signal...) then you need to capture many pulses/edges at a high rate, which takes up lots of memory. Even in a USB scope, this would be done internal to the scope device ( as opposed to sending the data to the PC, which has lots of memory) because the data sample has to go direct, at high speed, to memory, not via 'comparatively' slow USB

So, what I consider important in a scope -

Must have at least two channels. As high a sample rate as you can afford. DEEP memory. MUST have glitch capture capability if scope is 100MHz or less.

And last, BUT not least - A STANDALONE scope! Nothing is more frustrating that having to first power on the PC or the Laptop, just to use the scope. Or you want to measure some signals on the car's ignition, or your mate's electric train, and you have to lug the laptop, the scope, etc.

The scope is as I said as useful as a multimeter, and should be to-hand, and quickly available..Its like milling on the lathe - can be done, but what a lot of setup time - take off the top slide, get the vertical slide, bolt down, get the vice, bolt to the vertical slide, etc....Just go the the Mill and do it!

If you dig in my posts you will see I do a lot of electronics, and so bow to my scope quite regularly..

Sorry again for the lack of brevity..

Joe

Edited By Joseph Noci 1 on 12/08/2017 08:32:53

Neil Wyatt12/08/2017 09:21:22
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11870 forum posts
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I love my Hameg twin trace scope. I had my dad's Heathkit one in my teenage years/early 20s, then went for years without a scope until in desperation I made an add-on unit for my BBC micro, that only worked up to about 120Hz but got me out of a few holes. I finally got the Hameg second hand about fifteen years ago.

ANY scope is better than no scope.

I have heard much good feedback about the cheap digital scopes, get one of those it costs a pittance and will give you the chance to learn how to use it. If you decide if you need something more sophisticated, you haven't really wasted any money AND you will have a better idea of just what it is you want from more expensive kit.

Neil

Clive Foster12/08/2017 11:32:14
1156 forum posts
19 photos

Usually a mistake to go too far down market when you just want something to use and don't really have a feel for the various trade offs in performance and specification. Digital and software is great for getting lots out of a system relatively cheaply but you never know exactly whats going on underneath and digital on digital gives lots of opportunities for things to fall down the cracks. Analogue systems are straightforward, straight through so what you see is about what you get. Digital is different.

For microprocessor interface work logic analyser capabilities would seem a no brainer.

Tablet for a display seems a better idea than a PC as taking up far less space.

Scanning the USB / inexpensive digital scope market and comparing with the old time home shop lathe market I think we are still, so to speak, waiting for Myford. Most of the bits seem to be out there but the definitive combination hasn't yet surfaced.

My serious electronics days are but a dim memory but there is still a Phillips PM3252 and Tektroxix 2210 (early DSO) on the clean bench. Fastest Textronics 7000 series mainframe 4 channel storage 'scope up in t'loft if I ever get serious again. Twin timebases and about 8 amplifier plug ins in t'box. Most of the time an inexpensive DVM does the deed for ordinary electrical measurements but sometimes my AVO 8 is still the best way.

Neil's comment about getting a cheap scope to start with makes me wince pretty much like my piano tuner brother does when folk ask him about cheap piano for the kids to learn on. Skilled folk can work wonders with low end kit but you have to have a certain level of quality and capability in something to learn on. Fighting the limitations is mega frustrating. Especially if you don't know you are in a fight in the first place. Would help if there were simple beginners guide to getting going with practical exercises. All too often neophytes don't realise just how difficult something that looks as if it ought to be easy really is. Shades of the guys who bough a cheap MIG or MMA stick welder to fix the car!

Clive

Edited By Clive Foster on 12/08/2017 11:32:45

Edited By Clive Foster on 12/08/2017 11:34:48

Russell Eberhardt12/08/2017 11:58:04
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2077 forum posts
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Posted by Joseph Noci 1 on 12/08/2017 08:32:12:The scope is as I said as useful as a multimeter, and should be to-hand, and quickly available

I agree Joseph,

I made the mistake of giving away my HP Digital storage 'scope when I retired and moved to France. Several years later I bought a Siglent SDS1052DL which takes up far less room and does most of what I want.

However, the reasons I suggested a Bitscope for use with an Arduino were, cost, the ability to monitor and record a number of digital signals at the same time as two analogue signals, and of course, when experimenting with an Arduino, the computer is likely to be on anyway. I find it invaluable as a logic analyser even though I have a stand alone 'scope.

Russell

Swarf, Mostly!12/08/2017 11:59:09
401 forum posts
37 photos

Posted by Clive Foster on 12/08/2017 11:32:14:

SNIP

Most of the time an inexpensive DVM does the deed for ordinary electrical measurements but sometimes my AVO 8 is still the best way.

SNIP

Clive

Edited By Clive Foster on 12/08/2017 11:32:45

Edited By Clive Foster on 12/08/2017 11:34:48

Clive,

Regarding your AVO 8, have you got a solution for the scarcity of the battery (15 volts) for the high Ohms range?

Best regards,

Swarf, Mostly!

Clive Foster12/08/2017 13:42:46
1156 forum posts
19 photos

Swarf

Avo made an electronic step up voltage oscillator widget to replace the 15 volt battery. Got one in mine. Drains the main battery in about 3 or 4 years of storage. Which is probably not a bad thing. I might have a spare somewhere you could have. Don't hold your breath tho'. Got put somewhere safe, real safe. Haven't seen it for maybe 15 years so will have to wait for inspiration to strike.

Alternatively folk on t'net say its possible to make up a stack of button cells to fit in the space.

Clive.

Geoff Theasby12/08/2017 14:47:05
483 forum posts
11 photos

I'm late to this debate, but I believe I can add to it. I'm writing an article on these little scopes, having been a radio amateur for 50 years, in possession of a traditional (Philips) scope, and the author of other published articles on simple test gear using your computer sound card and downloaded software, mostly for free! Furthermore, I recently acquired an AVO 8, one of my life's ambitions. The difficulty of obtaining the right battery is of no consequence, since any cheap (£5) digital multimeter will be more accurate for testing resistors than the AVO. Surely most people have more than just the one multimeter?

Geoff

KWIL12/08/2017 17:02:13
2813 forum posts
50 photos

RVFM BLR154 15V Multimeter Battery

From Rapidonline, expensive but available.

 

 

Edited By KWIL on 12/08/2017 17:02:37

Neil Wyatt12/08/2017 19:59:31
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11870 forum posts
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Posted by Clive Foster on 12/08/2017 11:32:14:

For microprocessor interface work logic analyser capabilities would seem a no brainer.

It would seem so, but my mate Ray hacked the boot sequence of the Amstrad PCW using the Heathkit scope when designing an aftermarket disk interface for it...

Neil

Joseph Noci 112/08/2017 20:53:26
194 forum posts
496 photos
Posted by Neil Wyatt on 12/08/2017 19:59:31:
Posted by Clive Foster on 12/08/2017 11:32:14:

For microprocessor interface work logic analyser capabilities would seem a no brainer.

It would seem so, but my mate Ray hacked the boot sequence of the Amstrad PCW using the Heathkit scope when designing an aftermarket disk interface for it...

Neil

Mmm, Maybe...

But the clock on that processor back then could be measured in furlongs per fortnight...Even an AVO might have done the job...

Unless one is really strapped, or really not sure if the venture into micro's and the digital arena is for you, I cannot recommend basing down on such an instrument. Folk in the past have achieved wonders with very basic instrumentation, but that does not mean we have to worship Grandad's footsteps all the time - £400 or so out of the hobby pocket will hardly be felt after a few months - the frustration of a wasted £50-100 will be felt forever...

Let the Aurduino stuff frustrate and madden you, not the test instrumentation!

Joe

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