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

[lemon]

With an appropriate procedure this can eliminated. In the worst case will need to purchasing two boards (with some discount).

Can you please explain better this concept ??

I think, that you are member of "Electronics and Owon SmartDS oscilloscopes Forum".
At the two of these forums, there are discussions who described the issue very well and suggests methods or mods for eliminate this issue.
Methods with a short gnd distance or mods to main psu or adapter plate.
At pages from 51 and so on of this forum, you can find some of this methods and mods.

Sorry but my english, is very few to explained this better.

[luca1000]

I hope with new or future units don't need any mods.

The point that is it not clear and WHEN you can purchase a new unit without worries to ask the seller to test it before buy.

If there is a response about this question all problems are deleted.

[marmad]

My concern isnt' the gnd noise of this unit.
With an appropriate procedure this can eliminated. In the worst case will need to purchasing two boards (with some discount).

My concern is its fw.
Almost one year from bought this and there is a small improvement without fantasy and taking serious the various reviewer suggestions.
I have no see errors, yet and that's why I believed that is matter of time the improvement of sw.
Unfortunately time did not verified me.

Good hw but average sw!

Yes, IMO this is rather a problem with Owon. Forgetting for a moment the current noise issue, the SDS series has always been an interesting and well-thought-out hardware solution for the low-cost DSO market - and I appreciate that they've improved the HW in the two years since the series was introduced to Western markets. But from what I can tell, they've done very little extra work in the FW department (yes, I know they fixed some bugs, of course).

But considering all of the feedback from (and desires of) it's customer base that exist all over the Net, you would think that Owon might have added ONE important new feature - or even drastically changed the behavior of ONE old feature that customers didn't like.

Have they done this? Not that I've read about - although I could be wrong. Current owners are welcome to post information to the contrary.

OTOH, even Rigol - another Chinese company which is not very responsive to it's customers - has managed to, in their latest FW (for a product which is less than 1 year in Western markets) drastically change the behavior of a feature which many of us customers were complaining about.

I think Owon needs to rethink where they focus part of their attentions. Some times good PR (responding to customers desires) is as helpful to sales and good will as improving BW response by another db.

[Hydrawerk]

The Owon SDS series went to market in early 2011 and there are problems with noise even today, while 2011 scopes didn't have this problem... Well, buy Rigol instead. 

[marmad]

The Owon SDS series went to market in early 2011 and there are problems with noise even today, while 2011 scopes didn't have this problem... Well, buy Rigol instead. 

What are you adding to this discussion? You just seem to be interested in posting as often as possible to raise your number of comments. The members having this discussion are former/current/prospective owners of the Owon SDS DSO - of which you are neither. Of course, that wouldn't preclude you from contributing if you had some new perspective or information to add to the discussion - but that's not what you're doing.

[lemon]

GND Noise continuety...

At page 65 the member alexuresp shows an inside ferrite filtering the cable between main psu and adapter plate.
One other member found a small improvement by this method (I think that was Siri).
I decided to experiment about this with a clip cylindrical ferrite (see attachment photo).

My gnd noise is almost 145-160mV normal.
After this small mod the level noise was done 68-96mV! Eeep! This is not a small improvement, it is a huge! And all spikes has gone completed!
The next mod is more ferrites to probe (see attachment photo), after this the range of gnd noise is 38-56mV very well! (see attachment photo)
Also with only battery (no ac mains attached) the noise from 400mV drops to 106-110mV (see attachment photo).

[luca1000]

Very  interested !!

Do you think to try to find other "easy" MOD like this ?

The difference is HUGE, but a "normal" unit have less noise.

[lemon]

Yes the improvement is huge!

I don't know how is the level of gnd noise of the new Owon units. Probably the rf-loop can to feedback us.

Works very fine, look at vertical shift so that bottom of square can see. Very thin at 10M length!

I am waiting the opinion from more knowledge members than me.
I don't know if this is an exception that works only to me, but I am happy for the results!

[lemon]

I think the results is very well. I done a compare between "long gnd cable" and "short gnd"
------------------------------------------------------------------------------------------------------------------
Probe 10:1, Signal 10kHz, sine, 200mVpp, Probe connected to signal output and probe normal GND wire to signal source GND.

Probe 10:1, Signal 10kHz, sine, 200mVpp, Probe tip connected to signal output. Probe GND directly to signal source GND. (without "long" GND wire)

Probe 10:1, Signal 10kHz, sine, 30mVpp, Probe connected to signal output and probe normal GND wire to signal source GND (long gnd).

Probe 10:1, Signal 10kHz, sine, 30mVpp, Probe tip connected to signal output. Probe GND directly to signal source GND. (without "long" GND wire)

 

[rf-loop]

Good findings.

Yes with these methods can reduce noise but now need also note that "lemon" oscilloscope PSU and Adapter boards are different versions than this perhaps more "famous" later manufactured noisy version.

But blocking common mode high frequency noise, one important thing is "close" these noise roads with ferrite. This solution is "attenuate" noise. But still these circuits make this noise, only some roads are now "attenuated". 

Perhaps wise words: "do not make noise what then need attenuate or isolate."

But this method can use if want easy reduce this noise so that it do not so much pollute signal when use probe.

---------
How to regognize from total noise different fractions and where from these come.

There is simple method. (of course it need oscilloscope is opened.)
(testing  running scope internals need careful becouse this method use scope itself for this work)

There need two probes.

One probe, CH1,  for just tip and GND longwire connected to scope internal base plate (Z-plate) near main board side. Select V/div for good visible noise.

Other probe to CH2... take GND wire out and take hook out. Insert some isolation tube over probe tip and GND area so do not need afraid short circuit. (it is now just as capasitive probe.. it is enough for pick-up these noise spikes.

Select CH2 for trigger!

Take example PSU -7.6V SMPS  and pick up stabile trigger so that keep probe "capasitive" tip  example near this SMPS inductor or flywheel diode.

Look now CH1 signal... adjust horixontal speed for good visibility.  Now these peaks what are from this -7.6V SMPS are locked to trigger and other peaks run randomly... peaks what do not walk left or right on the screen are coming fronm this circuit.

With this method there can regognise all SMPS noise peaks... next TFT back light circuit on the adapter board ... and of course PSU board main flyback ...  CH2 probe near flyback transformer or secondary side double diode heatsink.

small exercise and find good settings...

Soon it can know what peak come from what circuit.

[TomC]

I don't know if this is an exception that works only to me, but I am happy for the results!

I've been thinking of trying this approach myself, but haven't opened the scope yet since it's only a few months old. Using ferrites to filter conductive noise and shields to isolate radiated noise is an approach used by manufacturers to salvage production boards that don't meet noise requirements. It doesn't fix a bad design, but allows their product to pass noise requirements without the expense of a full redesign. I would expect this approach to reduce the common mode noise of most Owon scopes suffering from the current noisy GND problem, not just yours. I have seen ferrites specifically designed to fit flat cables. When I try this approach in the future I will probably purchase ferrites of this type.

[rstoer]

Yes the improvement is huge!

I don't know how is the level of gnd noise of the new Owon units. Probably the rf-loop can to feedback us.

Works very fine, look at vertical shift so that bottom of square can see. Very thin at 10M length!

I am waiting the opinion from more knowledge members than me.
I don't know if this is an exception that works only to me, but I am happy for the results!

Good work Lemon! Although my unit predates the ones with the severe noise it still has some and I was thinking of trying this after seeing Siri's post. I'm sure I'll give it a try now.

[luca1000]

This is a big improvement !!

However can be interested if for example another ferrite to other internal part can "complete the work" or another "easy" mod.

[lemon]

...
---------
How to regognize from total noise different fractions and where from these come.

There is simple method. (of course it need oscilloscope is opened.)
(testing  running scope internals need careful becouse this method use scope itself for this work)

There need two probes.

One probe, CH1,  for just tip and GND longwire connected to scope internal base plate (Z-plate) near main board side. Select V/div for good visible noise.

Other probe to CH2... take GND wire out and take hook out. Insert some isolation tube over probe tip and GND area so do not need afraid short circuit. (it is now just as capasitive probe.. it is enough for pick-up these noise spikes.

Select CH2 for trigger!
...

With in my mind, what are suggest the rf-loop, I examined the main psu of my oscilloscope.
My psu version is PCB-T115-J REV6 with:
IC1 = R7731 Burst Triple Mode PWM Flyback Controller
IC2 = LM324L-S14_Quad Operational Amplifiers
IC3 = MC34063A-D 1.5A Step up_Step Down Inverting Switching Regulator

With the probe to air, the noise level is almost 218mV with a lot of spikes (see the first attachment photo).
With the probe 5cm over the psu board the noise is 510mV. A lot of psu rf noise (see the second attachment photo).
With the probe over to IC1 (see the third attachment photo).
With the probe over to IC2 (see the fourth attachment photo)
With the probe over to IC3 (see the fifth attachment photo)
With the probe over to switch J2 (a lot of noise) (see the sixth attachment photo).

What I am thinking about all these.
First I am thinking to apply a decouple filtering with Oscon capacitors between the vcc and gnd each IC.
Second I am thinking to make a metal safety cage that include the psu board.

What are you thinking about these?

[Hydrawerk]

Please use png for printscreens and keep them 800×600 pixels.

[TomC]

What are you thinking about these?

Your efforts and your willingness to share are appreciated, keep up the good work. Using good quality decoupling capacitors may help, a faraday cage as you describe may also be a good idea. Your posted images could be sharper if you used PNG instead of JPG. I use Irfanview free software to do the conversion from BMP to PNG.

[lemon]

There was a lot of compression with the conversion from bmp to jpeg. You have right the next images will be png.

I am thinking to change all the electrolytic capacitors (from what I have seen all of them are decoupling capacitors) with other with a low esr. The Owon used cheaper electrolytics capacitors here.

I'll come back with news...

[TomC]

There was a lot of compression with the conversion from bmp to jpeg. You have right the next images will be png.

I am thinking to change all the electrolytic capacitors (from what I have seen all of them are decoupling capacitors) with other with a low esr. The Owon used cheaper electrolytics capacitors here.

I'll come back with news...

Low ESR capacitors are good for audio applications, however, it's dubious if they will be of benefit for decoupling frequencies in the MHz range. But if you have some on hand you can try and see what happens. You may also want to try small mica capacitors in parallel, I've seen this often used to decouple high frequencies.

[rf-loop]

There was a lot of compression with the conversion from bmp to jpeg. You have right the next images will be png.

I am thinking to change all the electrolytic capacitors (from what I have seen all of them are decoupling capacitors) with other with a low esr. The Owon used cheaper electrolytics capacitors here.

I'll come back with news...

Low ESR capacitors are good for audio applications, however, it's dubious if they will be of benefit for decoupling frequencies in the MHz range. But if you have some on hand you can try and see what happens. You may also want to try small mica capacitors in parallel, I've seen this often used to decouple high frequencies.

This whole ESR "issue" is good to understand becouse too much hypes about esr...esr...esr...esr...
It need only once read one theory book and look real data about example different capasitors impedance/reactance curves related tro frequency.

As also it can see in DIY modification instructions version 2b.
(of course everyone can do own tests and also try how much low ESR electrolytic itself help but... perhaps there loose only time and material... but of course longevity may be improved using high guality electrolytics)

Specially there can see how 5V and 3.3V SMPS are bypassed (and note, both sides - SMPS input and output need!)  by ceramic capacitors and as near as possible also to reduce inductances on the board. And also, why parallel more than one... perhaps I did not have enough big capacitors. No. It is becouse different capacitor have different resonant frequency. Becouse I did not have in this point expensive good componenst for this, I use this method. And note, it was experimental work for find solution and also there was busy. (also in this time owon was waiting and need fast find some iportant keypoints for solve this problem. Then DIY version is derived from these experiments.)

[TomC]

Specially there can see how 5V and 3.3V SMPS are bypassed (and note, both sides - SMPS input and output need!)  by ceramic capacitors and as near as possible also to reduce inductances on the board. And also, why parallel more than one... perhaps I did not have enough big capacitors. No. It is becouse different capacitor have different resonant frequency. Becouse I did not have in this point expensive good componenst for this, I use this method. And note, it was experimental work for find solution and also there was busy. (also in this time owon was waiting and need fast find some iportant keypoints for solve this problem. Then DIY version is derived from these experiments.)

This is excellent insight on the many ways resonance or inductance of components (including printed ckt board traces) can influence the EMI of a circuit. I suspected you had some components stacked in the DIY because of this reason, but its good to post it so others know.

My scope is only a few months old, so I don't want to void the warranty with your DIY solution. When the scope is a little older and I trust the mayor components will survive the warranty period, I'll probably be more adventurous and try this solution. Lemon's scope is older and is already open because of a fan failure. So, I'm interested to see if he can improve the noise problem with solutions that are not likely to void the warranty, like ferrite cores and/or shields.

Personally I find the ground noise problem to be just an inconvenience. I only have to use the same probing methods and cautions that I would have to use anyway if the Owon was squeaky clean but the equipment under test was noisy. Still, I'm disappointed that Owon is unwilling to admit the problem publicly and offer a solution. I have contacted them via their chat/e-mail about this problem and they won't even respond. This attitude is not conducive to trust and good faith, which in their own words is supposed to be their motto.

[Armageddon]

I'm disappointed that Owon is unwilling to admit the problem publicly and offer a solution. I have contacted them via their chat/e-mail about this problem and they won't even respond. This attitude is not conducive to trust and good faith, which in their own words is supposed to be their motto.

It's a shame. I had another problem, I also contact them by email and did not even respond. 

"Meet your best need" 

[lemon]

It is very strange.
I had contact twice with them and their respond was very quickly!

The smd solution by rf-loop is the best approach to eliminate the gnd noise. He has investigate this solution and works fine! I have all electronic material and the appropriate technical knowledge how to do, but my oscilloscope is under of warranty and I am afraid!
Unfortunately, the Owon politic isn't clearly about this issue and how they think to offer us a solution in future.
If the offer will be a new psu and adapter board with some discount of course, for me there is no any problem to apply the rf-loop solution now.

I will experiment with some ferrite at the cable of boards and probes (I am waiting some of them) and I am thinking to make a Faraday cage by metallic mesh for the psu board.

[Armageddon]

They've responded only to some of my questions, respond according to their interest.
When the fan started to making a strange noise, I ask for a spare part and I got no response.
Even I offered paid the postage and the part, but nothing. 

I'm sure, a ferrite will help to decreasing the noise. I think too that a Faraday cage for the psu board, help.

rf-loop says: "do not make noise then what need attenuate or isolate."
I see it hard, if all DC/DC converters generate noise within the same band, it would be easy to filter (input and output), but this is not the case, and -7.6V SMPS need a better filtering.
This problem needs a total redesign of the main PSU and "power subcircuits DC/DC", including the TPS40222 on the main board.

I don´t understand to OWON, spending a little more would have been a good oscilloscope. 

I think that the smd solution by rf-loop is cheap, but not the best to eliminate the gnd noise, no doubt he has investigate this. But is OWON who should fix it, and offer a new psu and adapter board for free or with some discount, because many of us surely we would be willing to pay for it.

I don´t understand to OWON...

[Hydrawerk]

Well, it might be easy and cheap to buy a suitable fan. Or does Owon use a special one?

[rf-loop]

They've responded only to some of my questions, respond according to their interest.
When the fan started to making a strange noise, I ask for a spare part and I got no response.
Even I offered paid the postage and the part, but nothing. 

I'm sure, a ferrite will help to decreasing the noise. I think too that a Faraday cage for the psu board, help.

rf-loop says: "do not make noise then what need attenuate or isolate."
I see it hard, if all DC/DC converters generate noise within the same band, it would be easy to filter (input and output), but this is not the case, and -7.6V SMPS need a better filtering.
This problem needs a total redesign of the main PSU and "power subcircuits DC/DC", including the TPS40222 on the main board.

I don´t understand to OWON, spending a little more would have been a good oscilloscope. 

I think that the smd solution by rf-loop is cheap, but not the best to eliminate the gnd noise, no doubt he has investigate this. But is OWON who should fix it, and offer a new psu and adapter board for free or with some discount, because many of us surely we would be willing to pay for it.

I don´t understand to OWON...

This "do not make noise what then need isolate or filter" means that need design SMPS circuits with good design practices so that they do not produce noise.  This is primary rule. Secondary thing is then filter and isolate rest for make  real "silence". This is good rule for acoustic noise  (exaple motors) and for electronics, example PSU.

Example this experimental what I have done with PSU and Adapter board, it is only just some "what can do easy". It is NOT solution for this. These boards topology need radically change before it is good.

Today I do not know what kind is Owon new PSU what is going to mass production somewhere around start of June. And what changes they have made for adapter board (what is still more easy).

About fan. Just I heard one person who have bad fan and he call Owon and no any problem. Owon send new one.

If you have warranty failure in your scope, ask Owon start RMA procedure for get it repaired.
(in case that you have international "overseas" warranty.) Of course primary roadmap is contact seller. Why he sell these if he can not give any kind of after sales customer care. Or was he only "box shipper".  If this is case... you have get what you have paid. If example my customer is troubles (example failed fan) and if he want new fan from Owon and he want himself change it. If in this case Owon do not help him I take contact to Owon an ask this help to him. You know, all this is work. More or less.  But my customers have allready paid some amount of after sales customer care.

Common opinion
I wonder more and more this situation. Peoples buy from whoever box shipper example oscilloscopes. This box shipper seller do only that he receive boxes wrom some source and then he reship these to customers who buy. Then, what ever happends these customer are alone. Thenh all these customers want help directly from factory.

What other business go like this?  Buy bicycle... if troubles, who help... factory? If buy car, then some trouble... customer call with phone or letter to  factory who have made this car? ...  you buy Sony or Lg TV and then there is problem...  all peoples call directly to factory? 
Oh boys this do not work...   

Some yars ago I buy camera,  Canon..  then there was problem with it. Oh yes I send letter to canon factory secretary and ask factory help me. No no.
I call to seller and ask help. Kindly seller tell me how to do do.

I do not understand how this oscilloscope or other measurmenet equipments situation have gone to this position where we are now.

I have one recommendation to Owon. This is public recommendation.

Do not sell these equipments to "whoever".
Sell these only to these distributors who really also do they jobs and add some value to product. Product is more than only box. It include box itself but also some kind of pre- but more importantly some kind of aftersale customer care - even some amount.  Just like some brands do.

Stop  totally this wild markets!
Then give all and  full support for distributors - even some spare part lots. Even some teaching about products and some basic service information so that distributors really can give after sales support and add some value to product.

Organisation where all can be reseller (or better say: box shippers) and then all end users ask customer care from factory - in long run it is road to dead.  It do not work.  These box shippers can not give any value to end users. They make only finally this all business impossible.

If do not want this solution where all win. Triple win. Customer win. Dealer-distributor win and Owon win in long run. 

In other case it is best that only who sell these directly to end user is Owon itself.  And same recommendation to many other manufacturers. You need develop organisation.