REVIEW - Owon SDS7102 - A look at the SDS series from Owon

[Sarasir]

Hi TomC + +

I'm not so sure any more if it was my mods that caused the present problem I have: No Auto triggering - switching to Auto it will go back to Ready and stay there. I came to this conclusion because if I let it on running for an half an hour or so it slowly starts to auto trigger again and after about an hour it stays in Auto mode and time base is running but shows no input signal but HF oscillation like on both traces.

Obviously there is a thermal problem and it was comming slowly as I remember having seen that already long time ago but in the the beginning it came always back, but taking more and more time increasingly over the many days I'm tinkering with this thing now.

And I remember there was also a moment when I could do away with it by softly knocking on or even bending the main PCB a little as it seems.

Anyways, ordered another SDS 9202 yesterday to have a backup. I have checked the price for the TI ADC and it's about 1000$ plus german VAT and customs - and no samples of this available. That would be more or about the price for the whole scope here in Germany (1100.- €).

And I think my idea to get away with all switchers by connecting them with long wires to the scope was just unfinished thinking. This way I was creating an even bigger antenna for the opposite (to the BNCs) radiation side maybe not so much for the switcher noise but for the digital noise generated by the main PCB. I have overseen this completely. On the other hand by exploring the extremes often it helps to find the optimum some where in between.

Seems to become a very long story....

[TomC]

Hi Sarasir,

Sorry to hear this thing is still giving you fits!

If I understand correctly it only gives you trouble when in autotrigger and the other trigger modes work correctly. To me that sounds like something external to the ADC, probably in the main board, but not a faulty ADC chip in my opinion. Based on the warmup and sensitivity to vibration or bending symptoms I would look for a cracked circuit trace under a microscope or magnifying glass.

As far as spares, have you checked with Owon for availability and price for the main board? Hard to believe that the price for just a chip would be that high, no wonder Owon doesn't source from TI.

That's all I can think of for now. Let me know of any progress or new findings!

[Sarasir]

Hi TomC,

it doesn't trigger at all during warm up and as the ADC is the chip that gets hot pretty quick and as it also needs time for this heat to spread around to reach the foulty spot, I guess that this is also an indicator for that the problem is located somwhere else.

It's hard to scrutinize that board cause it's a multilayer and all blue and it could be everything in fact - cold soldering under a chip or bad contact inside a chip, whatever... with cracked traces to my eyperience you have to deal with rather in older machines (after many warm up/cool down cycles).

Also thought to get me a spare main PCB but first I prefer to get another new, complete and tested scope.

This will also give me the abibillity to do the 'oil-can-test' next - remember? - to get more, new and different experiences with the discussed phenomenons.

 ...and no stock of that chip over here in Europe only in USA one or two distributers have it...

[TomC]

Hi Sarasir,

Just wondering, have you thought of using one of those Freon based sprays to try to localize the problem area once the scope starts working after warmup?

Don't know what the "oil can test" is as related to electronics, I know they refer to that when testing metal for its ability to bend and regain its initial shape without braking.

[Sarasir]

....I mean to put the thing into an emty oil can (5 litres of greek olive oil was in before) and check if there is still radiation on the BNCs.... and what would the freon help? I used it for cleaning....and didn't know about that shape test - btw. sorry for my english...

[TomC]

....I mean to put the thing into an emty oil can (5 litres of greek olive oil was in before) and check if there is still radiation on the BNCs.... and what would the freon help? I used it for cleaning....and didn't know about that shape test - btw. sorry for my english...

I remember now about your plan with the greek olive oil can! For some reason 'oil-can-test' just reminded me of the metal test.

The Freon based spray (may be called something like Freeze-It) is used to quickly cool a spot on the board or a component, this often causes an intermittent or heat sensitive problem to reappear or in some cases to temporarily disappear.

http://www.chemtronics.com/p-778-freeze-it.aspx

By the way, I think your English is excellent!

[Sarasir]

Hi TomC,

I now now what you mean. Of course I have such a spray but didn't really feel to use it, rather a hair dryer to heat it up more quickly. Of course cooling it down then partly with the spray could perhaps reveal the area where this temperatur problem is located but what to do then? And I still think that the ADC might have suffered some damage as well because when the time base is running it still doesn't show the general input noise or any signal applied but only HF oscillation. So quite likely there are two problems, and one of them - the ADC - I'm not able to rectify at the moment.

Rather feel to get me another main PCB and replace it and use the broken one to trace down the circuit as there is no way to do that without taking off many components e.g the ceramic Cs for to evaluate them and also to be able to follow the traces somehow.

At the moment I'm shaping the oil can and I'm looking forward to what that test will show.

A soon as I know more I will post it.

[jaxbird]

It looks that newest FW (have been available from Owon some weeks) give max 260 wfms/s 
...
max 35 to max 260 is nice FW improvement without touching HW.

I can confirm, it does indeed look and feel a lot faster updating with the latest firmware update 

But actually sometimes I miss the old slower updates, as it would give a nice stable trigger on noisy signals without having to adjust the hold off  Guess you just can't make everyone happy. Nah, it's a nice improvement, a bit like a scope upgrade for free.

[radhaz]

What version is your firmware?

[rf-loop]

What version is your firmware?

Independent of what version read in Owon display after upgrade, version is this.


After update it may show example 3.8. -  this I have seen.   
 (but I do not know if some manufacturing patch show different version number after update)

Note: Do NOT even try for different serial numbers. If your serial is not in list then it is game over (can not).

(Before update be sure your USB connection with patch software works.
During update it need care that USB connection and PC continuous working do not fail/break.
(shut off all other works in windows what can any time do what ever.) 

SDS7102UP3.4
14-05-29 17:15:52

The firmware applied to the products with following production batch / serial no. -
SDS71021312xxx, SDS71021319xxx, SDS71021327xxx, SDS71021344xxx, SDS71021352xxx, SDS71021407xxx, SDS71021414xxx, SDS71021418xxx,

Change log - :
1. XY mode - persistence function added ;
2. waveform refresh rate improved ;
3.waveform cutting/ recalling function added;
4. autoset - waveform recognition;
5. channel invert bug fixed;
6. probe attenuation compensation;
7. recorded waveform exported to USB drive
8. automatic measurement - 4 more options available
9. vertical position over-speed movement bug fixed

(Before update be sure your USB connection with patch software works.
During update it need care that USB connection and PC continuous working do not fail/break.
(shut off all other works in windows what can any time do what ever.) 

[Antscran]

Hi all,

This thread goes on and on and on  , been browsing through most of the pages and have watched Marmad review and also Daves video look at the 300MHz version.

I am going to buy my first DSO soon and will be using for a multitude of projects, digital designs with SMPS using TI C2000 and other projects with the TIVA kit.

I have been looking at the Owon SDS7102V and also the Siglent SDS1102CML, both seem pretty capable and currently favouring the Siglent.  Curious if anyone has experience of the 2 or similar and how they would rate them.

I also noticed on page 162 of this thread Owon has released a new firmware, which seems to sort the refresh issue out.  Is Owon's customer service listening more and trying to resolve the issue that people have been talking about.

Cheers,

Ant

[jaxbird]

What version is your firmware?

Mine shows 3.8, but be aware the update is not available for all hardware versions, although mine isn't exactly new, it was included and the update is a nice performance improvement.

[radhaz]

In the About menu, mine shows 2.8.1.6

[TomC]

In the About menu, mine shows 2.8.1.6

If your scope is in the underlined serial number range that's what you are supposed to get. Apparently the hardware in that range doesn't support the new features available in firmware version 3.8. However, the same windows file (version 3.4) is used to upgrade scopes to different firmware versions.

[radhaz]

Ah, thanks for clearing this up for me. My SN is sds710211520, so I am current with my hardware.

[Sarasir]

Hi TomC + rf-loop,

just briefly, It works! The oil can around the Owon connected only to the input BNC makes almost all radiation disappear (Also added cores to the power cables of all gear used: Owon SDS 9302, Tek SG505 audio generator and Tek 475A 250MHz scope to monitor Owons input).

I dare to say that a plain sheet of metal does not act as a coil and therefore there are no reactances present created with stray capacitances as rf-loop predicted (as far as I remember).

Will take some photos of the set up and post them as soon as possible.

[TomC]

Sounds good!

If this is your new 9302, keep in mind that the new style PSU may be partially responsible for the experiment results. Will be waiting to see the photos!

[Sarasir]

....yes I noticed that the new one is remarkably better. Whereas my first one filled almost the whole screen with noise this one just fills less than half but that is still a bit too much.

Never the less, what I did is a simple before and after test, and I just noted the noise displayed on the 475A with the Owon not caged versus to having it caged...

The amount of reduction my experiment shows is what to focus on not the absolute readings I would say.....

[Sarasir]

Hi TomC ++,

so here my pics:

#1 : That's how it started, just the SDS9302 at 2mV/Div and the Tek SG505 with output on.

#2 : Same but just screen shot.

#3 : As #1 but SG505 output switched off.

#4 : As above but just screen shot.

#5 : Just Tek SG505 and 475A (at max sensitivity - 5mV/Div)  together.

#6 : As above, 475A screen shot only.

#7 : Tek SG505 and 475A with SDS9302 not shielded.

#8 : As above 475A screen shot.

#9 : As above SDS9302 screen shot.

#10 : Modified oil can.

#11 : Owon put into oil can - 475A screen shot.

#12 : As above - display detail version 1.

#13 : As above - display detail version 2.

#14 : As above but SG505 output Switched off.

Screen shots of the caged SDS9302 I will do after I cut a window in my oil can. And I think about some kind of metal grid to cover the window which then I can put on and off.

Perhaps I have one of this very fine meshes Tek offered as an option back then but have to search my stock - don't know yet...

The detail pics (#12+13) show very little residual noise on the peak of the sine waves after the Owon had to go into the can and the last pic also shows what's left of the spikes you can clearly see on both displays as long the Owon is 'free' (#7+8+9).

Last thing to add: The Tek 475A connected to the Owon 'swallows' a certain amount of Owons emissioned noise due to its solid mass some how (another effect for you to think about - I have no absolute clear picture yet because where does it go then? Perhaps is it just spread out more widely?). So for the moment its just the reduction achieved by caging the Owon that I can show (pics #7...9 versus #11...14).

So hope all pics are OK so far (turned 475A's intensity up to make anything in the backgroud visible but that also blurres the trace a bit).

[TomC]

Hi Sarasir,

Very detailed post with good photos!

My preliminary thinking is as follows:

I think it's possible that some of the noise is coming from an external source. Since the 475 is better shielded the noise is less apparent on its display versus a 9302 outside the oil can. The oil can provides shielding from external sources so when the 9302 is in the oil can the 475 reports very little noise.

I think it's also possible that the noise reduction when the 475 is connected in parallel to the 9302 may be due to the input capacitances of the two scopes also being in parallel. As a result more of the high frequency noise is dissipated reactively.

Let me know what you think of that hypothesis, like I said, this is just some preliminary thinking!

[Sarasir]

Hi TomC,

what you mean by external source? The time I made the pics no other noise was present with the Owon disconnected from mains (the terrible noise I had the other day never came back again after it disapeared the third day. Indeed must have been some HAM radio guy or whatever.).

All noise you see in the pics is generated inside the Owon, absolutely no doubt.

Theoretically the added 475 input capacitance of 20pF might reduce the displayed noise a little but I don't think that is significant. And the set up is the same with and without the oil can so why dealing with it?

The question why noise goes down when connecting the 475 to the setup was just btw. The same thing might happen as well if connecting a cubic of solid iron of 1m x 1m x 1m to the setup common ground. Must have something to do with the energy needed to drive a big mass - or antenna as well if you want - with HF.

Only the difference between the pics taken with the Owon in and out of the can counts in my opinion.

The displayed noise of the 475 shows just one snap shot of the noise due to it's more precise triggering whereas the Owon's display is rather unstable, has a tendency to trigger on different spikes each sweep.
But I haven't closely checked it's trigger abilities yet.

[TomC]

Hi Sarasir,

Based on the pictures and your description it's difficult for me to find a plausible explanation for the noise difference and exclude the influence of unknown, but real, external noise sources.

If all the noise was generated inside the Owon the oil can would block most of it from escaping from its confines. However, I don't see how it could prevent common mode currents inside the Owon from being converted to differential mode currents when faced with an impedance imbalance on the coax. So in my mind, a plausible explanation is the influence of the oil can over external noise sources, in other words, its ability to block most of the external radiations and prevent them from reaching the Owon. With an unshielded Owon the influence of external noise sources would account for an increase of common mode currents within the Owon and as a result more visible noise. The reverse would be true when the Owon is inside the oil can. On the other hand, the 475, which by itself registers very little noise, is built inside a metallic cabinet with probably better shielding characteristics than the oil can. This seems to be consistent in my mind with the theory that some of the noise comes from external sources.

There are a couple of other things that in my mind may play a part in the big picture. Inside the oil can the Owon's screen, a known emitter of near field radiation, is prevented from spilling it onto the environment. However, looking at the pictures, I don't see any of the coax cables close enough for this to be a mayor player on the experiment results. The other thing that comes to mind is the role that the points where you chose to ground the shield may have on existing common mode currents inside the Owon. By redirecting some through a potential shorter path there may be fewer available at the coax when faced with an impedance imbalance. However, without a way of visualizing these currents choosing the best grounding points may be a daunting task.

Anyway, let me know what you think!

[Sarasir]

Hi TomC,

I'm sorry my friend but I think you still have not got the big picture yet!?

Will give you another picture:

 When you heat up a pot with water and it starts boiling then steam is created. That steam will go into the environment, cool down, becomes water again that settles down wherever around.

With the above process going on the water inside the pot will become lesser.

If you had another pot filled with water placed on the same elevation level as the boiling one and connected both with a pipe at their bottoms then water would flow from the cold pot over to the boiling one (communicating pipes - physics!) - OK?

Now, if you would catch all steam with a cold shield the steam would condense and by conducting the condensed steam - now water again - back to the boiling pot you could take away the pot with the cold water because the water level in the boiling pot now would stay the same all the time - loop is closed!.

Now look at Owons emission! As long as they spread out 'new spikes have to be supplied' at our point of interest - the input BNCs (and it's exactly this point only because we choose it out of the fact that we want to connect something else to it that should not see what's going on inside!) - because the flow of emission must be counterbalanced due to the nature of this universe.

The moment all emissioned spikes are conducted back to this point all spikes are just running in circles but are not drawn ore pushed anymore from or into the outside world (An AC system here compared to the steam model which is a DC system - therefore I speak of drawn and pushed.).

What the oil can does is exactly that - catching all emissions of the Owon and conducting them back to the point we choose as the zero point.

Once more: It's closing the loop inside a system so nothing unwanted from the inside of that system can be seen anymore from the outside world!!! (In a way also a philosophical principle)

Have you got me now?

[TomC]

Hi TomC,

I'm sorry my friend but I think you still have not got the big picture yet!?

Will give you another picture:

 When you heat up a pot with water and it starts boiling then steam is created. That steam will go into the environment, cool down, becomes water again that settles down wherever around.

With the above process going on the water inside the pot will become lesser.

If you had another pot filled with water placed on the same elevation level as the boiling one and connected both with a pipe at their bottoms then water would flow from the cold pot over to the boiling one (communicating pipes - physics!) - OK?

Now, if you would catch all steam with a cold shield the steam would condense and by conducting the condensed steam - now water again - back to the boiling pot you could take away the pot with the cold water because the water level in the boiling pot now would stay the same all the time - loop is closed!.

Now look at Owons emission! As long as they spread out 'new spikes have to be supplied' at our point of interest - the input BNCs (and it's exactly this point only because we choose it out of the fact that we want to connect something else to it that should not see what's going on inside!) - because the flow of emission must be counterbalanced due to the nature of this universe.

The moment all emissioned spikes are conducted back to this point all spikes are just running in circles but are not drawn ore pushed anymore from or into the outside world (An AC system here compared to the steam model which is a DC system - therefore I speak of drawn and pushed.).

What the oil can does is exactly that - catching all emissions of the Owon and conducting them back to the point we choose as the zero point.

Once more: It's closing the loop inside a system so nothing unwanted from the inside of that system can be seen anymore from the outside world!!! (In a way also a philosophical principle)

Have you got me now?

Paradoxically, I agree with a lot of what you are saying, but at the same time, I also still agree with what I said on my post!

As you, I see the oil can (shield) as a means of confining the Owon's radiated emissions. As they encounter this barrier most of these emissions induce shield currents and as a result loose most of their energy while a few bounce back toward the Owon. So in that sense I agree that these unwanted radiated emissions from the inside can no longer directly influence the "outside world".

However, I don't think that the shield can provide a mythical or philosophical barrier that somehow corrals within its confines all the conductive common mode noise generated by the Owon. I can accept that It may short circuit some of it depending on the ground points chosen, but not to the extent that the inside and outside test results would require. So I still think that part of the noise visible during the outside test originates elsewhere.

In any case, regardless of the theoretical explanation, I think the experiment clearly demonstrates that shielding the Owon results in significantly better noise immunity. Whether all the noise originates within the Owon or whether it partially originates external to the Owon doesn't change these facts!

[Sarasir]

Hi TomC,

As to the aggreements just one example first: The 475 does exactly what it should do and that is to register whatever signal is applied to the center contact of it's input connectors referred to the sleeves (confined to it's specs of course).

... it's neither a mythical nor a philosophical barrier, it's a physical barrier. Just read again about the cage of Faraday... and if you want tell me about it's bandwidth limits. Haven't checked that yet I must confess.

...and now I do shout intensionally:

'THERE IS NOOO SIGNIFICANT OR RELEVANT NOISE PRESENT IN THIS ROOM HERE! SEEERIIIOOOUUUSLY!!!'.

Please, will you believe that eventually.

Do you really think I wouldn't notice that? (What you think Tek and before R&S and before Uher paid me for? For to be a bum or what? I have solved every technical problem that could be solved, sooner or later - some just needed a bit more thinking)

(I hope you still have kept your humor)