SDS7102 old stock serial identification (with noise issue)

[luca1000]

Hi,

Probably this question was posted different times in this forum and others but the situation it is not clear for me.

I like to purchase a new or used SDS7102 oscilloscope.

When I will ask to seller the serial number and the seller provide me it:

how I can be sure if the model hardware is or not affected to the noise issue ?

Actually the situation is not clear for me.

Here some serials:

1122xxx,1127xxx,1137xxx To V2.5.1.*

1143xxx,1149xxx,1152xxx,1153xxx,1203xxx,1209xxx To V2.8.1.6

1211xxx,1219xxx,1223xxx,1234xxx,1240xxx,1246xxx,1251xxx,1303xxx To V2.8.3


2 users with serials:

1149xx
12191xx

affirm to have the common noise issue hardware.

Please help !!!

[Armageddon]

Only make clear that probably all SDS models have this noise problem, since all these share the same PSU and adapter plate.
The new versions (recently assembled) have this problem fixed, but: Are these in the market? I doubt, for now.

Will send Owon spare parts to all with this problem? ... 

[luca1000]

I was asked this question to get a response.

You think that until now the new units are still have the problem  ... I hope no !!!

I hope that someone can we help for this ....

[Armageddon]

Who knows? I also hope that not. 

Why not also identify the serial numbers for SDS8102, SDS8202, ...?

[luca1000]

I hope that here someone can we do a full response about the SDS7102 model and the Others ...

I have more trust to real user instead of OWON factory.

[Armageddon]

Totally agree, but: 

How much noise must you have to consider that you have this problem?
And most important: What is this level to OWON?   

[luca1000]

I don't know exactly ...

The problem seem when you have small voltage signal.

Here there are some example:

http://owon.forumup.com/about159-0.html

apart this I don't know and I wating for someone that can have the response for we ...

[rstoer]

I apologize up front for the length of this post, but without proper explanation these screen shots would mean nothing.
Not all OWON SDS7102’s have a noise problem. Mine has a build date of week 27, 2011 and I would call its noise level quite acceptable for a scope in this price range. Some of the newer builds do appear to have a noise problem. I don’t know exactly when it started or if it’s stopped. I previously posted some screen shots of my ‘ground noise’ levels so I won’t repost them here but the values were about 4.8mV P-P with the bandwidth limited and 11mV at full bandwidth. Instead, here are some examples of ‘real life’ measurements which will hopefully substantiate my claim made in the first sentence of this paragraph.

All signals were generated by my Fluke PM5138A Function Generator. The oscilloscope probe was stuck in the BNC terminal of the generator for all tests. Because of the low voltage and 1KHz frequency of the signals being used for this test the probe was set to x1 with a short ground. The bandwidth was limited to 20MHz in 1, 3, 4, & 5.

The first two shots show the noise floor of the scope with no input:
1) Note the 1.2mV P-P reading with the bandwidth limited (20MHz).
2) Similarly note the 2.4mV P-P reading at full bandwidth.

3) This is a 1mV (.001 volt!) 1KHz sine wave. This is the lowest voltage my generator can output and almost assuredly lower than anything I’ll ever work with. I had some trouble triggering on it but you can see the P-P voltage is 2.16mV. If you account for the ~1.2mV of noise, this makes perfect sense. Note that even though the noise is larger than the amplitude of the signal it’s still useable.

4) Here I’ve doubled the amplitude of the waveform to 2mV. The scope can now trigger on it so you can see the frequency. Note the 3.2mV P-P reading perfectly reflects the 2mV signal and 1.2mV of noise.

5) Again I’ve doubled the amplitude to 4mV, and again the 5.2mV P-P reading perfectly equates. The point of the screen captures so far has been that the noise does not increase at all with the amplitude of the signal.

6) Now we get to some more realistic signal levels: 400mV. Of course, even this is too small a voltage to turn on most semiconductor devices. Although I’m still inputting a 1KHz sinewave I’ve opened up the channel to full bandwidth. I do keep the short ground lead for comparison to the next shot.

7) Exactly the same scope settings and signal input as shot #6 but with the standard (long) probe ground wire. The difference is small but still noticeable. Above one volt it became indistinguishable.

I think the above proves the point that not all SDS7102’s have a noise problem. I haven’t seen this kind of test on other scopes in this price range so I can’t compare, but this one works fine for anything I’d ever do.

[rf-loop]

Perhaps you have looked also these tests.

[luca1000]

If I have understand, there is no way to get 100% a unit without this problem becouse it is a random.

Until now the solutions seem:

1) Buy the unit to reseller that, before ship, do the hardware modification.
2) Use a short ground (this is not very useful/easy in real word).
3) Use a 10X probe and set the unit as "1X" (I suppose I need to divide to 10 each time).

I' am not a very expert, but in the market there is some special probe that can solve the problem ??

[rf-loop]

If I have understand, there is no way to get 100% a unit without this problem becouse it is a random.

Until now the solutions seem:

1) Buy the unit to reseller that, before ship, do the hardware modification.
2) Use a short ground (this is not very useful/easy in real word).
3) Use a 10X probe and set the unit as "1X" (I suppose I need to divide to 10 each time).

I' am not a very expert, but in the market there is some special probe that can solve the problem ??

1) I do not recommend this until know sure that seller can do this really so that he follow factory instructions how to do this or with other kind of good professional way. There is many kind of sellers! Do you like if some seller tell to customer that he have done modifications and then you find mod work is made by some entry level "garage floor barefoot soldering".

2) Probing is not easy "science". In entry level just good probing is perhaps most underlearned and underestinmated things. Good example was that just tikme ago I did measurements where it takes 3 days work for design and arrange how to take signal to oscilloscope. Then after all this "difficulty" or "not so practical" it takes 10 second to look this signal with scope and thats all. Three days work for just barely 10 second looking signal on oscilloscope screen.

3) What is the meaning of this?

[luca1000]

3) What is the meaning of this?

Here TomC suggest to use 10X probe
https://www.eevblog.com/forum/testgear/review-of-owon-sds7102/1065/

however if the problem can be fixed with a particular probe (or particular setting of probe) I like to know if is possible and what are the pros and cons.

[rf-loop]

3) What is the meaning of this?

Here TomC suggest to use 10X probe
https://www.eevblog.com/forum/testgear/review-of-owon-sds7102/1065/

however if the problem can be fixed with a particular probe (or particular setting of probe) I like to know if is possible and what are the pros and cons.

Yes, for make this test he explained. This is not for reduce this problems!


10x setting probe BW is full!  (so it can also better show this special noise)
1x setting it have typically 4-6MHz BW. (for test this noise this reduce too mmuch this noise what include spreads spectrum up to perhaps over 200MHz.)

IF you are looking low freq signals (and voltage is ok for 1x) and there is no harm becouse probe capacitance is now high you can switch probe to 1x and it may also work as low pass filter. It is highly dependent about test point characteristics.

But also, I'm much more iterested real signals testing that just looking what it show from scope own GND or probe compensation signal. I buy oscilloscope for test real signals. Probe compensation output quality is (if noisy otr not) enough for do probe low freq compensation. (becouse in these simple probes there is not any other but just this one compensation adjustment. In some other probes there is more adjustments (not for daily use and so they are under cover) and these need external signal sources for calibration)

Use 10x probe for more safe with higher voltages and for full BW.
If change oscilloscope itself probe setting 1x or 10x it do not change anything but displayed numbers. It do not have any other effect.

[luca1000]

Ok, I understand there is no solution to solve the problem.

So for this price range I can only "try" to buy an unit and hope to get a lucky to purchase a "non defected" unit.

Or consider another brand, but at this price the OWON "SDS7102" seem the best apart this risk ....

[rf-loop]

Ok, I understand there is no solution to solve the problem.

So for this price range I can only "try" to buy an unit and hope to get a lucky to purchase a "non defected" unit.

Or consider another brand, but at this price the OWON "SDS7102" seem the best apart this risk ....

I recommend:
Buy from seller who can make test!
Or local seller where you can your self test.
Later (timetable not available) Owon have new PSU version for SDS.
Example time ago I get ok units from Owon factory (perhaps from some kind of test lot of improved version but not information what time this version is fully in mass production). (it is tested and compared in other thread)
Just do not buy from "dropshipper" who only sell "nice boxes" if not like play lottery.

[luca1000]

Buy from seller who can make test!

If the seller don't know the problem, what type of test must do the seller and exactly what result I can consider positive or negative ? For do the test the seller must unpack the object ....

Later (timetable not available) Owon have new PSU version for SDS.

There is a way to get more informations (or updates) about it ?

I don't need the unit in this moment but certanly in the future.

another think:

If the seller affirm:

"Our units are fully working and came from factory and we don't sell "defected units". If the unit is defected you need to use warranty"

I suppose ignore the problem ...

[rf-loop]

If the seller affirm:

"Our units are fully working and came from factory and we don't sell "defected units". If the unit is defected you need to use warranty"

This looks like "dropship" seller or just "box shipper" seller.

These kind of sellers may sell all kind of boxes, some include parfumes, some box include tea, some include oscilloscöpe, some include teddy bears, and some clothes with many many different ebay accounts. They sell just what ever they get some money for eat. Many times they do nothing but ship boxes.

[luca1000]

Can I ask informations to OWON directly ?

Can I Trust to us ?

[Armageddon]

With all respect to rf-loop, sometimes you talk a lot but say little.

Answer this pelase:
 1. What noise level is right for OWON?
 2. Will send Owon spare parts to all with this problem?
 3. What items (s/n) are affected? And do not tell me that OWON do not know.

If you do not have answers then ask OWON...

[luca1000]

If you do not have answers then ask OWON...

I have sent an email to OWON, but franknly I don't know what type of response I can excepted and if it can be "true" ...

[Armageddon]

All have noise, the question is: How much noise is considered normal?

http://www.home.agilent.com/owc_discussions/thread.jspa?threadID=17549&tstart=105&start=45

http://cp.literature.agilent.com/litweb/pdf/5989-3020EN.pdf

[luca1000]

All have noise, the question is: How much noise is considered normal?

The noise that is consider "normal" is the noise that produce with a "short ground wire"

http://owon.forumup.com/about159-0.html

if there is "too much" difference between "short ground wire" and "normal ground wire" there is the problem.

If is possible fix this problem with some particular probe (I don't known if is possible), the problem is not very serious.

[rf-loop]

Here images including explanations.
This is normal Owon SDS7102V

There is test images where oscilloscope input BNC have clean signal.

There is also some test images made using normally (I mean this "easywork" practice)  Owon Probe with long GND wire.
(you can see also ringing what is made by "wrong use" of Probe. In professional world
if someone do this, it is exatly working error. (There is fast rising edge and people with total lack of any knowledge or experience use long GND wire and then think what is problem in my signal under test.  This is of course now here intentional mistake.  (and what ever signal use this GND wire in its pathway it need understand that it is reactive component. It IS inductor. 200MHz and its reactance is around 200ohm or even more. So, good bye tight GND. 

Oh well, some tell me that it is not very practical to use short GND. Yes I know, wrong measurements are more "easywork" to do than good measurements. We do many times lot of work for this... add probe adapters to PCB, solder short wires to PCB etc... just for some seconds looking oscilloscope display.

Here is not other kind of noise tests playing around with "probes".
But these images tell what is around normal noise levels when there is quite clean signal in oscilloscope input BNC.  What happend outside of oscilloscope, it depends so extremely lot of how people is working and what kind of skills end experiences he havé for do good quality measurements. These things are too much related to user. They depend how user use his tools and what he is doing.

 
This one image have Agilent 100MHz oscilloscope for compare.  Also copmpare is not so equal becouse in Agilent there was normal mode and lower samplerate, if do really compatible tests... Owon win more.

Agilent example inside  2nd picture  is from discussion: http://www.home.agilent.com/owc_discussions/thread.jspa?threadID=17549&tstart=105&start=45
It is copied from picture where is settings so that they can sure be very comparable with these owon settings here.



I do not take a position on what kind of results can be obtained with different measurement methods outside of the Owon oscilloscope. It depends so much about user. Here in EEVblog forum is mine and the others  many various test results with different measurement ways. All it takes is a little effort to look for them and read them.

Here normal Owon SDS7102V what I have today in my stock (new units from factory, arrived March 2013. )
I do not know what manufacture lot, what serial numbers may have or perhaps not this bad level "noisy GND" issue. My headache is whjat I sell. I'm responsible to my customers and only for them. If I now tell that this and that lot scopes I have... then someone think.. ok this is good.. then he buy from someone and big disappoint.. and finger show me.. you lie. So, I do not give information what may lead false conclusions. (end)

[luca1000]

Excuse me if my question probably is stupid:

If with a standard stock owon probe there is this problem, there is on the market a "particular probe" that can reduce this problem without use "a short ground" ?

I' am not an expert but the problem is clear for me but I serching for a solution, if exist, a "short ground" is a big compromise is not a "pratical solution".

Other scope don't need "a short ground" becouse the difference is near zero.

I hope exist an alternative  ...

If someone have some alternative , pratical solution , (not other informations about the problem that is clear for me), please share

[PA4TIM]

solution is easy, buy a better scope. But that will cost more. you can not improve a bad design with a probe. Non of my scopes have noise problems and I measure often signals under 1 mV. My probes are most from Tek. ( i have over 30 probes)

you have two topics about the same problem and I think you only hope to get one answer, buy that Owon. personally I do not like instruments that are not consistent in quality.