Oscilloscopes and cheap

[paulca]

No.  Oscilloscope + cheap = no.

I have ignored everyone telling me to spend money on the OSC and don't buy cheap.

I have ignored them 3 times and bought 3 scopes.  If I had of listened to them, waited, saved and bought a £500 scope, rather than 3 or 4 £100 scopes I still be better off.

Mistake one:
It's cheap, it says 50Mhz, if it does 25Mhz I'm fine.   Reality:  If it says 50Mhz and it's cheap, expect 5Mhz clear, 10Mhz barely usable and 20Mhz+ garbage.

Mistake two:
I only need to look at 1Mhz or 10Mhz I don't need RF non-sense!  A 20Mhz scope is fine.    Reality:  Your very next project needs 24Mhz to look at a high speed SPI interface.

Even if you get that 20Mhz and it is 20Mhz... you will grow out of it.  I now need to "see" 24mbit/s and 48mbit/s SPI communications.  At the current leading edge of the maker space, TFT screens close to HD and mobile screens from 10 years ago are now common on a breadboard.  ESP32s, STM32s are replacing Arduinos.  SPI and I2C coms on our breadboards are no longer running at 500Khz or 1MBit, but 25 or 50Mbit.... or higher.  20Mhz is useless.

The last scope I bought, after giving up electronics and wanting to get back in and not doing research first... was 100Mhz.  Yeapook.  ADS1014D,.  "100Mhz".  Nope.  It will do WS2812 1MHz perfectly.  3Mbit/s SPI fine..   Give it 24MBit/s SPI and it shows glitching offset sine waves and it's triggers and trace positions are messed up with DC offset, phase and attenuation.  Not to mention rendering artefacts due to software bugs.

If you are really new, just don't buy a scope.... or don't spent more than £50 on a "play" scope.

When you aren't "really new" and want to know why certain projects don't work, LISTEN TO WHAT THEY SAY!  Don't go a little higher in ££.  Go for the base, entry level, scope that has been reviewed, tested and does what you need now and what you will probably need soon.   It will save you time and money in the long run.

So even thought I bought a "This will work fine" scope a few months back.... I STILL need to buy a £500 rigol to debug my current project.

Spend the $50 on the "toy scope", play with it, sure. 

Realise the limitations and the problems with those devices.... then save money and wait... save.... wait for a sale/bargain and buy that Rigol or Keysight (etc) entry level scope which claims to be 100Mhz for £500, which will do far, far better than that £250 AliExpress 0.5GHz scope ... in the real word... measuring even 96MHz signals.

[Ground_Loop]

Maybe $800 really isn't too much for a hobbyist scope. 

[CaptDon]

Maybe don't buy bogus chinesium trash 'looks like the big name brand' garbage!!! Nothing wrong with dirt cheap Tek gear!! Pure analog stuff is o.k., 2215 etc. can be had in working condition with right-of-return warranty cheap enough. The Tek lunchbox scopes are very nice but more pricey. I paid $500.00 for a Tek TDS2004B and I love it!!! It can be hacked (with much effort) out to I believe 200Mhz. I picked up a TDS644B 500Mhz 4 channel color scope from the dumpster at work. The VGA output was working but the internal screen was blank. All it needed was a new crystal. The old one wouldn't oscillate. $5.00 fix for a scope worth over $1000.00  I generally rely on my analog scopes for most projects and repairs. The TDS644B rarely sees use and mainly for very transient signals or glitch detecting which it can do very well. No chinameese shit for my lab!! The reason I selected the TDS2004B was because a local manufacturer had nearly 100 of the similar models in daily use and only one ever failed in years of use!!

[bdunham7]

No chinameese shit for my lab!!

I'm sorry, but I just had to.   

[Doctorandus_P]

Aye, indeed.

If you're really on a tight budget, you can get a 2 channel scope for around EUR300, But I consider an oscilloscope a long term investment and would much rather go for the EUR 500 scope (With More channels, More bandwidth, More Memory, Faster acquisition rate, Ethernet, and lots of other stuff...

With a bit of luck it will last you 20 years, but even if it lasts only 50 years, that's still only EUR 50 per year.

I don't agree much with this though:

Spend the $50 on the "toy scope", play with it, sure. 

The trouble with that is that a lot of "beginners" are not able to recognize the limitations of their toy, nor interpret the distorted waveforms for what they are. On top of that, the input section of those those toys is often so bad that it's quite easy to damage them. The (quite old) DS1052E I have says on it's front panel that it's rated for 300Vrms, and normally it's used with a 10:1 probe and pretty much the only way to damage it is by putting lots of current through the ground lead.

On a side note:
I always wondered why the GND lead of oscilloscopes do not have built in fuses. You could make one yourself by just inserting a fuse in the "extra" ground wire with crocodile beak that all probes have. This may worsen HF performance, but for lots of measurements it's good enough and it may save your scope.

--------------
A long time ago, when I was young, I tried to measure how much current a wall socket could deliver into my DMM.
It did not work anymore after that, or, at least I thought so. The meter itself was not fused, but after some time I discovered that the copper of the test leads themselves had fused open, and the test leads were only held together by the plastic.

[CaptDon]

I am not sure what Chinese factory my Tek TDS2004B came from but they were mostly bullet proof and met specs with room to spare. Tek must have been riding shotgun on the quality control!! All of our locomotive circuit boards are being made in China and the quality is so poor we must burn-in and temperature test every board before using it due to poor quality and fake components that don't meet the far edges of the specs. AND we pay the board manufacturer to have already performed this testing. We used to send the bad boards back for repair, but they would come back to us with the same exact failure!!! Most of the old Tek stuff was good, but holy crap....those capacitor issues, not only on the TDS 5XX and 6XX but even the large electrolytics in the TM500 transport modules and the plug-in modules. I have had to re-cap a lot of those units to bring them back to life. The new Tek stuff sadly is cost prohibitive to anyone but the military or O.E.M.'s who can past the cost on to the customers!! That has really created the market for Chinese look-alike's (Agilent knock-offs) that don't meet spec's, have buggy software or simply are failed right out of the box!

[james_s]

No chinameese shit for my lab!!

I'm sorry, but I just had to.   

There's a difference between made in china and designed in china by some company nobody has ever heard of.

[tautech]

Maybe don't buy bogus chinesium trash 'looks like the big name brand' garbage!!! Nothing wrong with dirt cheap Tek gear!! Pure analog stuff is o.k., 2215 etc. can be had in working condition with right-of-return warranty cheap enough. The Tek lunchbox scopes are very nice but more pricey. I paid $500.00 for a Tek TDS2004B and I love it!!! It can be hacked (with much effort) out to I believe 200Mhz. I picked up a TDS644B 500Mhz 4 channel color scope from the dumpster at work. The VGA output was working but the internal screen was blank. All it needed was a new crystal. The old one wouldn't oscillate. $5.00 fix for a scope worth over $1000.00  I generally rely on my analog scopes for most projects and repairs. The TDS644B rarely sees use and mainly for very transient signals or glitch detecting which it can do very well. No chinameese shit for my lab!! The reason I selected the TDS2004B was because a local manufacturer had nearly 100 of the similar models in daily use and only one ever failed in years of use!!

Yet the only broken DSO ever had is a TDS2012B ! Fixed a few 210's and 1002B's as well yet not a single Siglent of the 100's we've sold.
Personal experiences are a strange thing and not commonly shared by others.
There's 3 Asian brands that won't be ignored in the coming decades, mark my words.

[paulca]

I don't think there is anything inherently wrong with the Chinese brands.  I don't think the quality is that low - for the price - either.

What does go wrong is in the characterisation of their products just isn't done, at all!  So they pick a FGPA or DSP for the core.  It says it can do 1Gs/s, so that immediately gets written on the box.  1Gs/s and thus 100Mhz.  The fact that they then apply heavy, heavy price pointing to all the supporting components and front-ends etc. etc. means it while it is technically sampling at 1Gs/s, those samples are riddled with analoge front end artefacts, phase, attenuation etc.  The 1Gs/s headline figure was for a single channel, but they have put 2 on the device which lowers that headline figure.  So you end up with a scope sold at 100Mhz 1Gs/s but when you try and actually use it, you find it's only even vaguely accurate up to maybe 20Mhz, 40Mhz if you put up with some distortion.

Obviously to that end, they don't test, characterise and declare what the scope will ACTUALLY do, they advertise and publish what it could theoretically do if everything was perfectly set up for it.... but will never happen in their product as they made it.

If I wanted an actual 100Mhz scope from a similar cheap brand, I would be looking at a 0.5Ghz labelled scope.

In reality I am looking at a Siglent 1204Xe via the 1104 hack route, or maybe just settle for a 1202Xe genuine.

The other factor to consider in my original story.  When I bought the OWON USB scope the only thing I needd to scope was Arduino digital projects and a few op amp circuits.

When I bought the latest 100Mhz (really 20Mhz) scope the only thing I had in mind was the likes of i2c, slow speed SPI and maybe WS2812 signals to scope.  Maybe some audio, maybe some power supply filters, you know.

But, your requirements change.  Above the 3rd thing I needed the scope for was debugging a 48Mbit/s SPI.  No chance.  Distorted phased sine waves with DC offset it all I got.  Even at 24Mbit/s it was barely usable.

No doubt if/when I fork out for the 200Mhz that should hopefully do the majority of that to a fair quality, being Siglent, I might find myself using 150Mbit/s SPI on 0.5Ghz MCUs. (That is actually likely).  My 200Mhz won't help with that, and my wallet is not willing to help with the money for 0.5/1Ghz scope!  At those speed, I would be better settling for a fast FPGA based logic analyser for digtal space.

[tautech]

In reality I am looking at a Siglent 1204Xe via the 1104 hack route, or maybe just settle for a 1202Xe genuine.

Do it, real good choice and far greater/better feature set than a SDS1202X-E. < They're a good little DSO but the 4ch feature set blows them away.

[Zenith]

Seems like a case of unpredictably growing demands and the wisdom of hindsight.

I'd have thought that if you were serious about wanting a benchtop DSO, the new market begins at about £300 for the low end Rigol and Siglent, which can easily be "reassigned" to be the top of the range. The market actually begins at just over £150 for Kiprim etc. Rigol and Siglent have support, particularly firmware upgrades, and a community of users on here, the lesser brands much less so.

My modest logic analyser needs have been met for several years with a £10 24MHz 8 channel USB unit from ebay. If I had a serious use for a logic analyser, it would involve some research and spending a lot more.

The other mistake, which is made less often, is to spend megabucks on equipment with capabilities you never use, and in any case, in five years time you will be able to buy one with those and new capabilities for less.

[nigelwright7557]

Don't get mixed up between bandwidth and samples/second.
One sample is one dot on the screen. Ignoring extrapolation.
So you need to divide samples by about 20 or 30 to get a displayable MHz.

I use a very cheap USB PC 3.3 mega samples dual channel scope I designed myself and it works fine.
Even has a spectrum analyser mode. Probably ok up to about 250KHz
Works fine for audio and model railway DCC signals.

[paulca]

Indeed.

On the LA.  I too have the little 24Mhz 8 channel "clone", works with PulseView.  It's only STM32s and SPI it won't touch, but I've learnt there is no shame in slowing the prototype down to get it working, then speed it up and...well... hope.

It's also wise not to dismiss some little gems you can find from AliExpress.  Not ALL of it is over-sold, underspeced.  I have been very pleasantly surprised by the 4xUSB QC2.0 5V Buck modules I bought about 3 years ago.  So much so I bought another one recently.  They claim to put out 3A at 5V across all ports.  However, I have run a laptop off one of them and all it did was got a bit warm happily supplying 20 Watts to the laptop for a few hours until I felt sorry for it being a little desk heater.    Other than that they could use a bit of hot snot to stop the inductor wine at low current. 

Relating back to LAs.  There are a few CPLD/Sub-FPGA ICs out there with open source firmware to run 16 channel LAs on them at ... more than 24Mhz.  I'm still trying to find an answer on just how fast, but it seems as though, with it being an FPGA style affiar, that's sort of up to the user and how hard they want to push it.  The FX2 boards are easy to find, but there is firmware out there for the FX3 apparently written (and the board open sourced) to present a firm middle finger to Saleae.  I've not found a pre-made FX3 board yet, but there are dozens of the FX2s with the firmware preflashed on Ali for £15.

I realise a lot of these boards are clones of open source or less than open source projects.  Small time makers, make an excellent board design and sell it for £20 on Tindie.  2 months later the boards are on AliExpress for £3.99 in their 10s of thousands.  Poor maker is shut right out of his own market, but ... we get cheap, and possibly faster tech!  It's a dog eat dog world.

[paulca]

Don't get mixed up between bandwidth and samples/second.
One sample is one dot on the screen. Ignoring extrapolation.
So you need to divide samples by about 20 or 30 to get a displayable MHz.

Yep.  And Nyguist says nothing about visualizing or anything other than a sine wave at 1/2 sample rate.

I was tending on thinking a minimum of 10 samples per period, although, if you start to consider the "desired" rising edge performance, you need to be looking it's frequency component and not the main signal.  A 1Khz square wave out of a 150Mbit/s SPI port has a rising edge frequency component well into the Ghz.  It will look completely incorrect on a 200Mhz scope and probably a 0.5GHz one at that!  Anyway, it is a bad example.  The digital 1s and 0s is LA territory, unless your basic line encoding is buggered, then you are on your own without a high end scope... or just accept your place as an amateur and above 100Mhz you are in YMMV territory anyway where the analogue side will start to become a factor much more with trace impedance and all that lovely stuff.

[paulca]

In reality I am looking at a Siglent 1204Xe via the 1104 hack route, or maybe just settle for a 1202Xe genuine.

Do it, real good choice and far greater/better feature set than a SDS1202X-E. < They're a good little DSO but the 4ch feature set blows them away.

I did it!  I did the thing!  I wasn't going to, but Amazon happened to mention I still had 0% interest installments option available.  The way I looked at it... my Mother and Brother are asking what I want for Christmas and I know they can't afford the scope, so I bought it for myself, from them... I'll let "them" know about that later.

Arrives Monday.

Now I regret binning the packaging of the DS1014D.  Pretty sure it was still in it's return window, but not without the original packaging, unless it were to become faulty.... and I'm too honest for that.

[Terry Bites]

RF nonsense? How very dare you!

Bandwidth is one thing- you need to think about the features you will need.

[paulca]

RF nonsense? How very dare you!

Bandwidth is one thing- you need to think about the features you will need.

RF to me involves "Greek" symbols.  Of which I know what about 3 mean.  It's all calculus and trig and horrid equations or your stuff not only doesn't work, but means the neighbours Wifi doesn't work either! 

Such it's "nonsense" to me.  I try to avoid what I can't ignore.

On features I'm still reading what the new one does.  A feature I really needed this week was a delayed trigger.  I knew the first byte on the wire was fine, there was a problem with the second.  Could I get the scope to capture the second byte?  Nope.  So I glanced at the trigger modes on the 1104 and wow.  I think the DS1014D has edge and level and nothing else.  I think delayed triggers or even pattern match triggers should solve that if I dont just go straight to the serial decode mode.

[pcprogrammer]

You can always use the ADS1014D as a project. There is a FPGA in there one can play with, two ARM MCU's,  a display and a bunch of knobs and buttons.

There is already a lot of work done to dissect the thing. https://github.com/pecostm32/FNIRSI-1013D-1014D-Hack

Good for may hours of joy 

[james_s]

I don't think there is anything inherently wrong with the Chinese brands.  I don't think the quality is that low - for the price - either.

What does go wrong is in the characterisation of their products just isn't done, at all!  So they pick a FGPA or DSP for the core.  It says it can do 1Gs/s, so that immediately gets written on the box.  1Gs/s and thus 100Mhz.  The fact that they then apply heavy, heavy price pointing to all the supporting components and front-ends etc. etc. means it while it is technically sampling at 1Gs/s, those samples are riddled with analoge front end artefacts, phase, attenuation etc.  The 1Gs/s headline figure was for a single channel, but they have put 2 on the device which lowers that headline figure.  So you end up with a scope sold at 100Mhz 1Gs/s but when you try and actually use it, you find it's only even vaguely accurate up to maybe 20Mhz, 40Mhz if you put up with some distortion.
willing to help with the money for 0.5/1Ghz scope! 

In other words it's junk and the manufacture cannot be trusted to provide reliable specs, that in my opinion is something that is inherently wrong with these brands and the reason I would not give them my money. I don't want to reward dishonesty, I will not buy something with grossly exaggerated specs.

[rstofer]

In other words it's junk and the manufacture cannot be trusted to provide reliable specs, that in my opinion is something that is inherently wrong with these brands and the reason I would not give them my money. I don't want to reward dishonesty, I will not buy something with grossly exaggerated specs.

The naysayers have tested the hell out of the Rigol DS1054Z and after a few firmware upgrades, have finally shut up.  It does what it says it can do and, when unlocked, has the -3dB point at 130 MHz.  This has been proven as fact!  There's a mega-thread over in Test Equipment.

It did take a couple of years to get it right (there was a persistent, if comical, misspelling) and the newer Siglent SDS1104X-E (unlocked to 200 MHz) is probably a better buy.  But there is nothing wrong with the Rigol that I know of.

I don't know anything about the other scopes in the various families so my reply to "what should I buy" always comes down to the DS1054Z and the SDS1104X-E.  The -U variant of the Siglent is just stripped down to a price point.

New users should be required to watch Fourier Series of Square Wave videos before being allowed to buy a scope.  No, you can NOT see a 100 MHz square wave on a 100 MHz scope.  To have anything resembling a square wave, the frequency probably can't exceed 10 MHz (this would give us the 3rd, 5th, 7th and 9th harmonics).  The rise and fall should start looking pretty good with the 9th harmonic in the trace.  Still not perfect but good enough.

Put a 50 MHz square wave into a 100 MHz scope and all you'll get is a sine wave because the 3rd harmonic is beyond what the scope can display not to mention trying to display higher order odd harmonics.

[james_s]

The naysayers have tested the hell out of the Rigol DS1054Z and after a few firmware upgrades, have finally shut up.  It does what it says it can do and, when unlocked, has the -3dB point at 130 MHz.  This has been proven as fact!  There's a mega-thread over in Test Equipment.

I'm not talking about the Rigol, my friend has one that I've used and I was suitably impressed, it's a low cost hobbyist oriented scope that has honest specs and provides a lot of bang for the buck.

The scopes I'm talking about are the less reputable brands, the Aliexpress specials and such that don't even come close to their rated specs.

[paulca]

I don't think there is anything inherently wrong with the Chinese brands.  I don't think the quality is that low - for the price - either.

What does go wrong is in the characterisation of their products just isn't done, at all!  So they pick a FGPA or DSP for the core.  It says it can do 1Gs/s, so that immediately gets written on the box.  1Gs/s and thus 100Mhz.  The fact that they then apply heavy, heavy price pointing to all the supporting components and front-ends etc. etc. means it while it is technically sampling at 1Gs/s, those samples are riddled with analoge front end artefacts, phase, attenuation etc.  The 1Gs/s headline figure was for a single channel, but they have put 2 on the device which lowers that headline figure.  So you end up with a scope sold at 100Mhz 1Gs/s but when you try and actually use it, you find it's only even vaguely accurate up to maybe 20Mhz, 40Mhz if you put up with some distortion.
willing to help with the money for 0.5/1Ghz scope! 

In other words it's junk and the manufacture cannot be trusted to provide reliable specs, that in my opinion is something that is inherently wrong with these brands and the reason I would not give them my money. I don't want to reward dishonesty, I will not buy something with grossly exaggerated specs.

Have you ever tried to buy desktop speakers for a PC?  You would be infuriated with specs like 1500W but a PSU spec of 100W.  PMPO and RMS not even mentioned.

[james_s]

Have you ever tried to buy desktop speakers for a PC?  You would be infuriated with specs like 1500W but a PSU spec of 100W.  PMPO and RMS not even mentioned.

No, but I've had a few sets of those pass through my hands, they're junk. I've always used a regular stereo amplifier and some bookshelf speakers. There are some halfway decent powered speakers that don't have bogus specs too.

[tautech]

On features I'm still reading what the new one does.  A feature I really needed this week was a delayed trigger.  I knew the first byte on the wire was fine, there was a problem with the second.  Could I get the scope to capture the second byte?  Nope.  So I glanced at the trigger modes on the 1104 and wow.  I think the DS1014D has edge and level and nothing else.  I think delayed triggers or even pattern match triggers should solve that if I dont just go straight to the serial decode mode.

These are the times the retriggering rate catches you out when we need to apply a trigger Holdoff for the length of the whole packet which then will provides rock solid edge triggering for which you can then use HPos to examine the complete packet.

Member Charlotteswiss brought the cheaper SDS1202X-E and we explored the complete feature set starting here from her purchase:
https://www.eevblog.com/forum/beginners/what-an-oscilloscope-recommended-for-a-woman-passionate-about-electronics/msg3104228/#msg3104228

That thread because basic operation of SDS1104X-E is the same will provide great guidance until you get into the fruits the 2ch models don't have.

[james_s]

Something worth keeping in mind is that scopes like the Rigol and presumably Siglent hold their value really well, on multiple occasions I've seen used Rigol scopes sell on ebay for *more* than it cost to buy a brand new one from Tequipment even before you factor in the eevblog discount. Actually sold, not just the inflated asking price, I don't get it but it happens. If you take good care of it you should be able to sell it for close to what you paid if you change your mind or find that it is not a good match for your needs.