New 2ch pocket DSO+SG - Zeeweii DSO2512G

[Aldo22]

FYI, I measured a bandwidth of approximately 35Mhz on my scope in normal mode.
When in overclocking mode, the bandwidth increased to about 40Mhz then the signal dropped off.  However, around 80Mhz the signal level increased and I was able to get to 120Mhz measured & displayed on the internal frequency counter.

Hi 4thDoctorWhoFan!
Are you aware that this device has different "bandwidths" depending on the settings?

2 channel/standard mode: ~48MHz
2 channel/OC mode: ~60MHz
1 channel/standard mode: ~96MHz
1 channel/OC mode: ~120MHz

Going beyond these limits will show bs.

You can turn on/off the second channel by long pressing button "CH1/CH2".
You can turn on the overclocking mode with Menu Aux + ⇧ (long)

[radiolistener]

Hmm, but then why does it look much better without a load resistor, only connected directly with coax?

Without load resistor there is no proper matching and your cable turns into a filter which distorts the waveform. It doesn't looks better, it just have waveform distortion and you see incorrect waveform. Probably it attenuates high frequency components, so you cannot see high frequency details on the waveform.

2.02Mhz looks almost the same as with the probes and 9.9MHz has some jitter but it looks much smoother than with load resistor.

Probably there is some issue with displaying waveform which consist waveform with sharp high frequency details. When you remove dummy load or add probe instead of coax cable, it leads to impedance mismatch and waveform distortion, so it may remove waveform details by smoothing it. And such smoothed waveform is displayed more stable.

It's unclear why it happens. Proper oscilloscope should always work as expected and show nice waveform with coax cable and dummy load. This is why I don't recommended to buy such devices, because you never know why it don't works as expected and stuck on fighting with it's bugs.

it is possible to do investigation to find the root of cause for such behavior, but it needs to check impedances up to 1 GHz and use good source with known waveform. Unfortunately there is no guarangee that your si5351 module works the same as other. For example it may use fake si5351 chip which has a little different characteristics and produce a little different waveform. But I think si5351 is ok, probably there is some issue in DSO software to display waveform with very sharp edges...

Did you tried to check amplitude  (RMS and pk-pk) for si5351 output on different frequencies at wide range? Amplitude should be the same. If it has significant chage this is a sign that there is impedance mismatch. Try it with different configurations.

Also try different cable length, if it leads to amplitude change, there is a sign of impedance mismatch.

With proper connection amplitude should be the same, regardless of cable length and frequency.
For original si5351 module it should be about 1.5 Vpp = 0.75 Vpk, and about 700 mVrms.

PS: forgot to say - also, make sure that you set SI5351_DRIVE_8MA (=3) for SI5351_CLKx_CTRL register. It will setup max amplitude output for si5351 CLKx output.

[Aldo22]

Did you tried to check amplitude  (RMS and pk-pk) for si5351 output on different frequencies at wide range? Amplitude should be the same. If it has significant chage this is a sign that there is impedance mismatch. Try it with different configurations.

The screenshot series above was taken using the Si5351 but with a probe.
https://www.eevblog.com/forum/testgear/new-2ch-pocket-dsosg-sigpeak-dso2512g/msg4783148/#msg4783148
As far as I can see, the amplitude drops relatively evenly and about as expected from 3.2 V to 2.6 V.
Unfortunately, I don't have any device other than the toy-dso to measure this.

For now, I'll put the Si5351 to rest. The TinySA will arrive soon, then I'll see more.

Thank you!

[radiolistener]

Aldo22

Try the following test: use different frequency and measure Vpp and Vrms voltage with different connection. Put it in the table and publish here. It will be more easy to analyze.

For example:
Frequency |  coax | coax+load |  probe | probe+load
1 MHz
2 MHz
3 MHz
4 MHz
5 MHz
6 MHz
7 MHz
8 MHz
9 MHz
10 MHz
11 MHz
12 MHz
13 MHz
14 MHz
15 MHz
16 MHz
17 MHz
18 MHz
19 MHz
20 MHz

[Aldo22]

Aldo22
Try the following test: use different frequency and measure Vpp and Vrms voltage with different connection. Put it in the table and publish here. It will be more easy to analyze.

Thank you!
I'll probably do that over the weekend.
I'm too busy today.

[tatel]

@aldo22

Probe cable isn't the same as coax cable. You could  watch Dave's video from 17:00 forward.

Long history short, 50 ohm terminator is to be used with real coax, not with the probe.

If you use real coax without termination, you get signal reflections because you have low output impedance (about 50 Ohm) on your sorce and high input impedance (1 MOhm) on your scope = impedance mismatch.

Switchable probes are optimized to work at 10x attenuation. Attenuation comes from voltage division between 9 MOhm resistor on the probe and 1 MOhm resistor on scope input. Now if you throw your 50 Ohm terminator in the middle, you get funny things.

Probe is designed so at 1x there's no impedance mismatch with scope's 1 MOhm input impedance. Again, if you put a 50 Ohm load in the way, you get funny things.

The fact that impedance is frequency-dependent allows for even funnier things.

Your scope should work fine with coax + 50 Ohm terminator at 1x attenuation. If it doesn't, then there's something wrong with either your settings, your signal source or your scope.

I have been missing information about the amplitude given by your signal source. DSO154 shows bigger amplitude at higher frequencies. The opposite should be true. It's not the most stable thing I have seen, either. DSO2512 looks the same to me, althought it will probably be at least 2x better, I hope.

I hope things will get better once you get TinySA, it should be better as a signal source. But please make sure it's settings are OK.

[4thDoctorWhoFan]

FYI, I measured a bandwidth of approximately 35Mhz on my scope in normal mode.
When in overclocking mode, the bandwidth increased to about 40Mhz then the signal dropped off.  However, around 80Mhz the signal level increased and I was able to get to 120Mhz measured & displayed on the internal frequency counter.

Hi 4thDoctorWhoFan!
Are you aware that this device has different "bandwidths" depending on the settings?

2 channel/standard mode: ~48MHz
2 channel/OC mode: ~60MHz
1 channel/standard mode: ~96MHz
1 channel/OC mode: ~120MHz

Going beyond these limits will show bs.

You can turn on/off the second channel by long pressing button "CH1/CH2".
You can turn on the overclocking mode with Menu Aux + ⇧ (long)

Yes, I am aware of the different modes.
Like I said in my previous post, I get 35Mhz bandwidth in 1 channel/standard mode & about 40Mhz in 1 channel/OC mode.
I was using a 1Vrms input signal and adjusted the frequency until the amplitude dropped 3dbm to about 707mvRMS.  Connected using a 50ohm coax with a 50ohm load.

[radiolistener]

si5351 module is very nice test signal source. Because it has 1 ns rise time and can provide any frequency from 10 kHz to 200 MHz. Original si5351 module has 1.5 Vpp output for 8MA CTRL register config.

But there is also possible fake Chinese chips which can have some issue. So all Chinese things should be checked

[Aldo22]

Thanks for all replies.
As I said, I don't have much time for testing and watching videos today.
Only briefly: The SigGen breakout is a $4 one like in the attachment.
I don't know how to test if it is a fake.

Thank you!

[Aldo22]

Hi
I'm still trying to understand why this little $80 toy oscilloscope is considered so incredibly bad -> crap -> not worth even $20.
Of course it's very limited, but aren't other devices too?

I happened to come across a review of another device.
It is a device for €400, which is five times as much as the DSO2512G.
https://www.peaktech.de/PeakTech-P-1265-30-MHz-2-CH-250-MS-s-Digital-Speicheroszilloskop-mit-USB-LAN/P-1265
Sure it's built better, has more features and a bigger screen etc. but that wasn't the point.

With this device at 20MHz, you cannot see any real difference between square and sine wave (Red line in first picture on the page linked below).
The author says you can't stabilize the signal at 30MHz and it shows a ghosting (last picture on the linked page).
https://www.elektormagazine.de/news/review-digitales-oszilloskop-peaktech-1265/15883

Why is this 5 times more expensive device considered better in terms of the displayed signals?
I mean the DSO2512G can show a difference between sine and square wave even at 40MHz.(Attached image).
As a layman, I don't understand the level of contempt, or should I say hate, shown towards this toy.

[4thDoctorWhoFan]

Well, I don't consider it crap.  For the price, I think it's real handy and quite like it.

I knew from the start the bandwidth was not going to meet stated spec but I am happy with my 40Mhz measured bandwidth.
For a cheap, small & throw in a bag gadget, I think it's worth it.

[radiolistener]

It is a device for €400, which is five times as much as the DSO2512G.
https://www.peaktech.de/PeakTech-P-1265-30-MHz-2-CH-250-MS-s-Digital-Speicheroszilloskop-mit-USB-LAN/P-1265
Sure it's built better, has more features and a bigger screen etc. but that wasn't the point.

With this device at 20MHz, you cannot see any real difference between square and sine wave (Red line in first picture on the page linked below).

I cannot recommend that PeakTech either. Because it's goal is to have an appearance resembling a normal oscilloscope. The main indication of that is that it has just 250 MS/s which is smaller than 1 GS/s which is a minimum for a modern digital oscilloscope. I don't know how that PeakTech works, but I'm sure it also has similar issues.

The difference between normal oscilloscope with such toys is that normal oscilloscope allows you to use it for measurements. And toys doesn't allow it. For example you can just connect signal with coax cable and pass-through terminator to a normal oscilloscope and it will show you proper waveform and amplitude.

For comparison DSO2512G can't measure it. And the reason why it can't is unknown. You already learned it.

So, you can get normal oscilloscope and just use it for your job with no needs to fight with strange issues. And no needs to invent solution on how to use it to measure, say the amplitude. You can just get it and use it and it doing what it should do.

With a toy you can play with it like with a toy, but can't measure something and can't be sure that it shows proper waveform. That's the difference.


If you want to do a real tasks with oscilloscope, you're definitely needs a normal oscilloscope. And if you're want to buy DSO, it should have at least 1 GS/s sample rate. It should have real 1 GS/s, not marketing lie. This is not because 1 GS/s is cool, but because there is no sense to manufacture fake oscilloscope with a real 1 GS/s ADC. If manufacturer put 1 GS/s ADC on device, it probably has expertise to implement proper oscilloscope, at least it has expensive equipment for such manufacture. When manufacturer put 250 MS/s ADC, he doing it because he don't have expertise to work with more serious electronics, such device can be made by some student in the home on a knees.

For example, the devices such as DSO2512G can be sell as a DIY kit, because it can be soldered by a newbie amateur at home and it don't requires expensive equipment for tuning it.

If you're want just to see some random waveform on the display, and no needs to be sure that this waveform corresponds to the signal that you put on it, and no need to get proper measurements. You can use a cheap toy.

But for 80 USD you can buy a nice old school second hand analog oscilloscope. It allows you to see proper waveforms, allows to do proper measurements and sometimes it even allows to do things which is not available on low end DSO, such as Siglent or Rigol. So, if there is no enough money for a normal low end oscilloscope, it's better to buy old school analog one. Old school analog oscilloscopes was made for a longer lifetime than modern electronic devices.

[Aldo22]

@radiolistener
That's clear to me and from a professional point of view you're certainly right.

I just don't understand why you're so obsessed with the DSO2512G.
There are so many other devices on the market which cannot do 1 GS/s.

You make the DSO2512G look like the worst crap ever screwed into Chinese plastic.
But it is always to be seen in relation to the price.

The difference to the PeakTech is that for the €400 it costs you would get an almost decent new oscilloscope, while for the $80 you won't get anything else, except second hand maybe but I have no room for such a heavy, clunky old thing.

I understand your technical reasoning, but I don't understand your "special" emotions towards this cheap little toy.

Thank you!

P.S. The TinySA will arrive tomorrow. I'll report back.

[radiolistener]

I just don't understand why you're so obsessed with the DSO2512G.
There are so many other devices on the market which cannot do 1 GS/s.

I added explanation above. 1 GS/s ADC needs more serious skills for design circuit that use it, also it needs to have more serious and expensive equipment for solder, test, debug and tune it. ADC which has less than 1 GS/s doesn't needs deep knowledge and it's easy can be soldered even by newbie amateur at home, because it has simple QFP or SOIC package which can be soldered with a usual solder iron. This is why there is so few fake devices based on 1 GS/s ADC or with higher sample rate.

The difference to the PeakTech is that for the €400 it costs you would get an almost decent new oscilloscope

I don't understand why someone buying PeakTech for €400, because you can buy Siglent for such price (at least I remember someone on this forum bought a new Siglent for just 350 USD). Probably these buyers just don't understanding what they are buying...

And by the way, this is not decent oscilloscope. At a glance it looks like yet another clone of FNIRSI 1014D.

I understand your technical reasoning, but I don't understand your "special" emotions towards this cheap little toy.

Previously I was catch on that marketing and bought such a cheap devices, but later I realize that it was mistake and it worth to buy normal equipment, even if it cost more. Just want to help other people to not catch for these tempting traps. If someone had explained this to me at one time, perhaps I would not have spent extra money on a crap and bought something worthwhile.

P.S. The TinySA will arrive tomorrow. I'll report back.

I don't want to upset you, but I think it would be better to spend money on NanoVNA instead of TinySA. NanoVNA allows you to measure antennas and impedances. TinySA is intended to show the spectrum. Do you really needs to analyze spectrum? If so, it's better to buy RTLSDRv3 and use it with software such as HDSDR. It will cost you about 20-30 USD, but give you much more things to learn and you can use it as SDR receiver, which allows to receive almost any radio. I guarantee that you will be very satisfied with RTLSDRv3 and it allows you to learn a lot of a new things.

[Aldo22]

Previously I was catch on that marketing and bought such a cheap devices, but later I realize that it was mistake and it worth to buy normal equipment, even if it cost more. Just want to help other people to not catch for these tempting traps. If someone had explained this to me at one time, perhaps I would not have spent extra money on a crap and bought something worthwhile.

I understand and thank you for trying to warn people.
However, I look at it a little differently, because for me the device delivers what I expected and for the time being I'm also satisfied with what I can do with it for the price paid.
I think testing the si5351 via coax is a somewhat academic matter for such a toy. Nevertheless, I will take a look at it with the TinySA SG.

Actually it's enough for me if I can measure something with the probes, because in practice I don't have any SMA connections on the test objects.
For me, the second channel is interesting. I didn't buy it primarily because of the bandwidth (or fake bandwidth).
But there are 200KHz oscilloscopes on the market which also cost $30 after all. In this case I would also say that this investment makes no sense.
These cannot even display a 100KHz square properly.

I don't want to upset you, but I think it would be better to spend money on NanoVNA instead of TinySA. NanoVNA allows you to measure antennas and impedances. TinySA is intended to show the spectrum. Do you really needs to analyze spectrum? If so, it's better to buy RTLSDRv3 and use it with software such as HDSDR. It will cost you about 20-30 USD, but give you much more things to learn and you can use it as SDR receiver, which allows to receive almost any radio. I guarantee that you will be very satisfied with RTLSDRv3 and it allows you to learn a lot of a new things.

Thank you, but it's too late. 
I could buy NanoVNA later if i see any purpose. It's costs even less than TinySA.

Thank you.

[Aldo22]

The difference to the PeakTech is that for the €400 it costs you would get an almost decent new oscilloscope

I don't understand why someone buying PeakTech for €400, because you can buy Siglent for such price (at least I remember someone on this forum bought a new Siglent for just 350 USD). Probably these buyers just don't understanding what they are buying...

And by the way, this is not decent oscilloscope. At a glance it looks like yet another clone of FNIRSI 1014D.

I think we mean the same thing here.
Something got lost in translation.
I also thought that for €400 you could buy a decent oscilloscope, which this PeakTech is not.

[tunk]

At a glance it looks like yet another clone of FNIRSI 1014D.

Most likely a rebadged Owon (maybe SDS5032E).
The price is on the high side.

[Aldo22]

Btw. I certainly don't want to hijack this thread, but since we're talking about PeakTech:
I actually stumbled across the review above because I was looking for a test of the P-1404.

This model seems to have better specifications and is relatively cheap.
That's why I was surprised that there are no reviews to be found about it.
Is this also sold under another brand?
Do you think it's crap? 
Don't worry I won't buy it.

[tatel]

@radiolistener:

If you can get me a good, working one, with reasonably easy-to-find spares, dual-channel, one of them invertible, 20 MHz analog scope that can be delivered to my door for €150, no matter if you got it for $80 or for free, I'm ready to pay that to you, just send me a private message and a Paypal link.

@aldo 22

Some background, available to you, in my previous post about aliasing. Follow the link.

Signals have harmonics. Particularly square waves *need* to have harmonics or hey couldn't be square. These would be, I think, higher order odd harmonics. So a square wave at 10 MHz does have higher frecuency components that would be 3x, 5x, 7x the main frequency, and so on. These harmonics have increasily lower amplitudes. Please see this animation: https://youtu.be/cUD1gMAl6W4

Now, to sample a signal, Nyquist theorem says you need to take samples at at least 2x the frequency, or you wouldn't be able to reconstruct that signal with any fidelity. Worst case, if you don't know signal phase, you will need to sample that signal at least at 4x the frequency because of, well, aliasing. I think these sine waves you showed at 60 MHz show aliasing, because I doubt your signal source puts out a different amplitude at each cycle.

Now, Tektronix et al will say to you that 2,5x the frequency will be enough if you use sin(x)/x interpolation to reconstruct the signal from your samples. Anyway, it's expected that your device will be able to filter higher frequencies that could make aliasing appear, because they can't be sampled at least 2x, 2,5x, 4x, whatever, their frequency. So, to fight that aliasing, you need an anti-aliasing filter, that is, a low-pass filter that cuts frequencies higher that some cut point. That filter could be as simple as an RC network.

Now, probably you already understood that radiolistener is being more papist than the pope. First of all, that statement about needing to have at least 1Gsample per second or else you have a toy. I can't agree with that. Even without antialiasing filter, a device will be good enough up to some frequency. It's just that the device would be only good up to a quite lower frequency. Please correct me if you can prove I'm wrong. I would love to know.

I usually consider the frequency where a square wave becomes a sine one, to be a good rule of thumb about a device's bandwidth. That happens because the scope can't cope with the higher odd harmonics anymore.

That said, no scope is able to show a square wave up to its advertised frequency, at least in our hobbyst price range, I think. But radiolistener has a point, a serious device should have an antialiasing filter. To put in the market a device able to do 100 Ms/s without putting an atialiasing filter to cut off frequencies above 25-40 MHz would be an incredibly stupid thing to do IMO. We all know for sure DSO2512 can't be trusted up to 120 MHz. But, if it doesn't have any antialiasing filter, it can't be trusted even at 25 MHz even if it does sin(x)/x interpolation. So, a device that could be good to do some low-end but serious work, like looking at PSUs, becomes a toy. I wouldn't buy that device for a $100. I already have my €40 DSO154 as a toy to learn just the more basic things. I would look instead for something that can reliably work at 20 MHz, even if the price is 2x that of DSO2512.

I'm afraid the purpose in going to market without antialiasing filter could be only to scam newbies. As radiolistener said, that way you could claim you have higher bandwidth, but it would be no more than a scam, and a incredibly stupid one because it makes a potentially useful device just a toy. Thinking nobody would be able to notice it is even dumber. So there could be some base for comptent, yeah.

But before throwing any comptent, DSO2512 should be carefully tested to seet what it's good up to. That's never academic. I hope that, once TinySA comes to you, we all will know the truth, should you be willing to do these tests.

[tunk]

I actually stumbled across the review above because I was looking for a test of the P-1404.

That's most likely a rebadged/reworked Owon SDS1102 which you should be able to get cheaper elsewhere.

[tunk]

I would look instead for something that can reliably work at 20 MHz, even if the price is 2x that of DSO2512.

You could take a look at the handhelds from Owon (e.g. HDS242) and Hantek (e.g. 2C42).

[wasedadoc]

That filter could be as simple as an RC network.

Simple RC filters should not be used in situations where the waveform shape is important. Such RC filters are not linear phase.

[tatel]

I would look instead for something that can reliably work at 20 MHz, even if the price is 2x that of DSO2512.

You could take a look at the handhelds from Owon (e.g. HDS242) and Hantek (e.g. 2C42).

At first glance it looks good, a 40 MHz, 250 MSa/s advertised device, with a 20 MHz bandwidth limit, for about €125 on banggood. I guess we can assume it would be good to look at PSUs. I'll have to read more about it before pulling any trigger.

https://es.banggood.com/OWON-HDS200-Series-2CH-Handheld-Oscilloscope-40-or-70-or-100MHz-Bandwidth-20000-Counts-Multiumeter-OSC-+-DMM-+-Waveform-Generator-3-in-1-Suitable-for-Automobile-Maintenance-and-Power-Detection-p-1802427.html?rmmds=detail-topright-recommendation&cur_warehouse=CN&ID=6301777&trace_id=6cb91682085368224

I'm not sure about banggood. They sent me two dead-on-arrival  Best hot air rework stations on a row. Third one was good. Not the only thing that came to me from banggood in a broken condition. https://www.eevblog.com/forum/reviews/best-bst-863-hot-air-station/msg3610430/#msg3610430

I have to say, Banggood solved the problem acceptably. However note that you could have to send the broken device back to China even if you bought it from any european warehouse. Chinese customs are very finicky. If you forgot to include any documentation, item will be retained at customs. You'll have your money back, but if you paid by PayPal, your returned money will got Paypal's cut, too. So a little money lost and quite a hassle.

That said, at the end I do have a good-working hot-air station, and spares seem to be the same as for Quick.

This very same approach should be used by Zeeweii, a cheaper, 20 MHz reliable device would be enough for me. I already have a benchtop 100 MHz scope, so 40 MHz bandwidth is not a big advantage over 20 MHz to me, portability aside

And Digikey lists this ting at $259 so I could go with Banggood again after all...

[tatel]

Simple RC filters should not be used in situations where the waveform shape is important. Such RC filters are not linear phase.

I'll take that. Perhaps a couple resistors+ a couple caps + an op-amp could do?

[wasedadoc]

Simple RC filters should not be used in situations where the waveform shape is important. Such RC filters are not linear phase.

I'll take that. Perhaps a couple resistors+ a couple caps + an op-amp could do?

Linear phase requires inductor(s) as well as capacitor(s).  Either actual inductors or techniques such as gyrators. (https://en.wikipedia.org/wiki/Gyrator)