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

[Teneyes]

Here are two captures, one of them is "gnd noise" and the other the same time what is appearing the FFT...almost 100MHz.

Yours has almost even noise from about 80MHz to 140MHz. , but the noise in my scope peaks at 100MHz unlike yours.

Hey Guys,
That looks like FM Radio Stations,
Maybe try it in Faraday cage,  metal Filing cabinet w/screen on front

[luca1000]

What do you think about an "alternative ground tip" like this:

http://www.ebay.com/itm/100-Pcs-Silver-Tone-Connector-Clasp-Ball-Chains-Keychain-Tag-10cm-3-7-8-/251276885018?pt=US_Unisex_Accessories&hash=item3a8144fc1a

can reduce the noise on Owon SDS7102 ?

[lemon]

Here are two captures, one of them is "gnd noise" and the other the same time what is appearing the FFT...almost 100MHz.
The test was done by Owon probe.

Thanks a lot for the images. From your FFT image I can see that the noise on your scope is a little different than mine. Yours has almost even noise from about 80MHz to 140MHz. That explains to me why you don't see much difference using lower input capacitance probes. Here are some similar images from my scope using both the stock Owon probe and a 9.5pF input capacitance Tek probe. As you can see the noise improves with the lower capacitance probe, but the noise in my scope peaks at 100MHz unlike yours.

From what I have seen the noise is depends from schema of Probe Cable.
The probe cable is working like antenna and catch everything!

Because my english is not well, here is a video with above thought. There is a noise profile and how this changed by schema of probe cable. At the same time an fft seems the same thing...

My top of noise curve is under of 100MHz (almost 90MHz) and the pattern is don't like yours.

The test was done with Owon Probe and very quickly without any warming of unit, because I have an open unit because failure of fan. If you wish I can take two captures by an other probes.

What do you think about an "alternative ground tip" like this:

http://www.ebay.com/itm/100-Pcs-Silver-Tone-Connector-Clasp-Ball-Chains-Keychain-Tag-10cm-3-7-8-/251276885018?pt=US_Unisex_Accessories&hash=item3a8144fc1a

can reduce the noise on Owon SDS7102 ?

Tips like this reduce the noise per 90%. As ground clip as close to probe tip, the noise is decreased.

[TomC]

From what I have seen the noise is depends from schema of Probe Cable.
The probe cable is working like antenna and catch everything!

Because my english is not well, here is a video with above thought. There is a noise profile and how this changed by schema of probe cable. At the same time an fft seems the same thing...

My top of noise curve is under of 100MHz (almost 90MHz) and the pattern is don't like yours.

The test was done with Owon Probe and very quickly without any warming of unit, because I have an open unit because failure of fan. If you wish I can take two captures by an other probes.

Yes, part of the noise is radiated and part of it is conductive. There is a lot of radiated noise around the scope's TFT panel, so when the probe cable is near the panel a lot of this noise is visible. Also, when you touch the cable with your hands your body becomes part of the antenna with both capacitive and inductive components. As a result the visible noise may increase or decrease depending on how you hold or arrange the cable. Some of the noise you see when holding the cable is not necessarily originating from the Owon. I have several computers in my electronics shop and I can see this noise change depending on my location in respect to the computers, specially laptops with external Switch Mode Power Supplies.

Regardless of whether the noise is radiated or conductive, all I see is common mode noise converted to differential noise when a long ground lead is used with the probe. The radiated noise can be avoided most of the time by keeping the probe cable away from the Owon and other noise sources and avoiding touching it. If this is not possible, sometimes I use ferrite cores on the probe cable to decrease the influence of the radiated noise and a little of the conductive noise. But none of this is usually required if a short ground is used. Here are some images illustrating some of this:

1. The effect of having the probe cable next to the scope's TFT panel with no ferrite cores on the probe cable and using a long ground.

2. The effect of having the probe cable next to the scope's TFT panel with no ferrite cores on the probe cable and using a short ground.

3. The effect of having the probe cable next to the scope's TFT panel with ferrite cores installed on the probe cable and using a long ground.

4. The effect of having the probe cable next to the scope's TFT panel with ferrite cores installed on the probe cable and using a short ground.

5. Illustration of the Owon scope probe with ferrite cores installed on the cable and the fixture I used to connect the probe's tip & ground ring to the scope ground.

[luca1000]

Teorically a good probe must be shilded to prevent any interference (EMI) ??

Why the ground wire have often (or always)a thin section and not a robust section to help the conductivity and shielding ?

P.S.

I see an interested article that affirm that if you apply a ferrite on AC power supply cable this can reduce the common mode noise. Someone can test it with the the Owon SDS7102 ??
 

[TomC]

Teorically a good probe must be shilded to prevent any interference (EMI) ??

Why the ground wire have often (or always)a thin section and not a robust section to help the conductivity and shielding ?

P.S.

I see an interested article that affirm that if you apply a ferrite on AC power supply cable this can reduce the common mode noise. Someone can test it with the the Owon SDS7102

The probe's coax wire used is a compromise between appropriate shielding and practical size and flexibility that you can get with available materials. If you used very large gauge wire and shield you could get better common mode rejection, but is not practical. Usually this is not a problem since the scope's input amplifier is designed to respond to differential signals only, so the common mode noise, as long as it remains common mode, is invisible to the scope's input amplifier. When you add other components to the coax wire, e.g. a long ground lead, the external reactance causes an imbalance and part of the common mode noise gets converted to a differential signal. Once it is in differential form it will be visible on the scope.

The long ground wire is intended for low frequency use and is made thin and flexible for ease of use. For low frequency applications you can use other means for reducing noise such as limiting the bandwidth and/or using average mode. There are special ground adapters that use low inductance conductors for high frequency applications. But these, by necessity, are usually small and not flexible. I have experimented with designing a longer low inductance ground wire for my convenience. One approach I used was using de-soldering wick, which is flat, as a conductor. However, the benefit was small because I couldn't reduce the inductance enough to make a big difference.

I have tried one or more ferrite cores on the Owon's power cord to reduce common mode noise produced by other nearby equipment from entering the Owon. In my particular environment, the only time this made a difference, is when I had a very noisy switch mode power supply connected in the same outlet as the Owon.

[onlooker]

Ferrites on probe cable act as low-pass filter. For higher frequency use, short ground tip is to be used. 

[TomC]

Ferrites on probe cable act as low-pass filter.

I'm curious. Have you tested this? If so, at what frequencies did you find this effect? I have compared the frequency response of the probe with ferrite cores illustrated on my previous post with an identical probe without ferrite cores. Through the frequency range I used for my test, 30MHz to 110MHz, the response was identical. So, at least, in this frequency range, there is no low pass effect for differential signals. Of course, if you are talking about common mode noise/signals, I agree there is a low pass effect. But then, that is the point of using the ferrite cores, to help block high frequency common mode noise.

[luca1000]

Someone have tested the difference with inside battery (Owon have it as optional) or eventually plug the AC oscilloscope cable on UPS for PC ?

There are opinions that affirm the common mode noise can be decresed on some of this ways ...

[lemon]

Mine SDS7102V has this optional and the result is worst!

Look at the attachments captures.

[luca1000]

At this point the problem seem independent by the power supply if with battery is worst...

[rf-loop]

At this point the problem seem independent by the power supply if with battery is worst...

No.

I recommend you take some time now and really read all information about this issue and filtrer also out all this "information" what only mix and shake this case.
Also it is good to read some amount theory for understand these things so that all is not so much just "magic" things.

If "lemon" show this last image so that mains power is disconnected and scope run using battery, situation and noise is different.

With battery AND mains power together produce more noise and this noise component what rise is main PSU flyback circuit noise.

I repeat it agen here and agen with some different words.:

Inside scope there is several noise sources. And all noises is conducted to different parts with radiation and conductice, common mode and differential mode. And for understand full case it need understand about RF fields and how RF trawels in different cases and circuits.

Noise "sources":

main PSU
8.4V main PSU flyback converter (1). (severe noise source)
(nominal 8.4V  but around over 6V up to to 8.4 if battery) This is master power line and from this is all others derived.
If mains power line is out, battery give this voltage   

(1) this is off if only power source is battery.

sub SMPS circuits: (voltages not exactly)
-7.6V (severe)

Adapter board
+5V (moderate - severe)
+3.3V  (it seems that this is moderate or less)
TFT back light SMPS (severe)

All these generate  high frequency noise   in these units what can name real "noisy GND" problem units.

Every these noises have some amount different signature.

All these can separately detected and analysed as example I have done.

These highest  spikes in "lemon" last image come exactly from main PSU running flyback converter what produce 8.4V from example 230V Ac or what ever is connected to mains power line.

(these spikes also vary dependent of battery charging sitiuation but they are always more high if battery is installed and powered by mains. (in problem units)

If we look externally oscilloscope whole GND it have sum of these noises and it all is (what are meaningful noises) RF noise from some MHz to over 200MHz. And this we can look that it is "common mode noise". Simplify... it can think that scope GND area works like you have transmitter and it is its antenna. Now you connect wire to  it... there start flow RF current to this wire and also it is now part of this "antenna" network. it radiate (meand current flow) and it conduct to places where it is connected... and current flow... etc
But all wires have inductance.  You know what happend when RF try go via inductance.... it produce voltage over it...

Oscilloscope probe have also wire..  this coaxial from BNC to probe tip.  This RF noise travel via this probe cable and then it travel via this probe separate GND wire and it continue its travel forward to where you have connected it. Important  is that in this point where scope probe GND wire is separated (this blacl 15cm wire)  there is now This RF travel over this GND wire and RF  produce  voltage over this GND wire. Yes... this GND wire is short copper wire. How its ends have differet voltage... it is nearly zero ohm. For 100 or 200MHz it not at all "zero ohm..." if it is thinn or thick,, no big change.. if it is gold or iron.. not big difference.. you can coat it by silver.. no big difference (in this case).  But if you make it more short... it change radically its inductance and so also reactance.  Ferrite over power cord.. yes it is useful but not for this what this probe do. And you can take 1000 euro brand name high-end passive proble and it is more noisy in this case..

Yes your DVM show zero ohm over this short GND wire.  But... this wire is inductor...it is coil (without turns) every wire is .. 1cm or 10m have inductance. Independent of if it is cheap Owon wire or expensive Rolls-Royce wire or Tektronix wire.

This RF flow over this wire and it produce voltage over it! And what our oscilloscope show, it show voltage diffrencies between probe tip and probe GND. If you think keep tip in zero potential tightly  and then you run signal to GND wire... oops what you see... you see signal.

If think ferrites on power cord or some other place it need understand how they work and how this noise itself.

Primary solution is reduce this noise there where it is produced. (repair these SMPS circuits what are guilty for this)

Secondary solution is try reduce its affect to measurement = do not externally connect this signal to signal under test. And here we can do it with short GND and also get some more help using ferrites over probe coaxial. (2-3 turn thru ferrite example.  It may block some amount of this RF noise flow from scope GND via probe cable to probe tip end.

perhaps "lemon" can show how this second picture how it change if take power cord out and run with battery alone.

This proofs that with battery assembled and used with mains power situation is more bad tah mains alone without battery os with battery alone without mains power.

[luca1000]

If "lemon" show this last image so that mains power is disconnected and scope run using battery, situation and noise is different.

I must suppose yes, otherwise what type of test is this ?? Don't have sense ...

I' am curious about this.

[alexuresp]

Long time did not visit the forum.
I looked around the circle are the same questions that have been resolved for another 60 pages.
It is clear that the device is a toy and no one at the factory will not fix noise. There is a scheme for modification from rf-loop and there is no nothing difficult. The issue of noise is closed by soldering 10 items.

rf-loop is there statistic how many users have repaired noise by themselves?

[Hydrawerk]

This scope might be good, but always test it well before buying.
This means never buy from eshops!

[luca1000]

To rf-loop,

If I have understand to solve definitively the problem is suffcient replace the mettalic pillar with an equivalent nylon pillar as showed on the picture ??

Seem very easy if is true.

No other actions need ??

 

[AndrejaKo]

I'm not rf-loop, but I have answer to that:

What you have is instruction on how to solve noise only on channel 1 for some older units from the end of 2011. On newer scopes, the pillar is already nylon and current issue is not channel 1 noise issue.

[rf-loop]

To rf-loop,

If I have understand to solve definitively the problem is suffcient replace the mettalic pillar with an equivalent nylon pillar as showed on the picture ??

Seem very easy if is true.

No other actions need ??

may I ask what is idea for mix and shake.

This was old  totally different case. This is for OLD  CH1 noise issue what was looong time ago solved by Owon and after then I do some help instructions for some peoples who want do this themselves. 
This problem start when Owon change  whole front end construction and example in lab tests it did not show this noise at all. (if it was disassembled as service run position)

Soon there come information about CH1 special noise. Nearly as soon as it was finded Owon find solution in they test lab.  (inside shielded front end metal pillar connects  to very sensitive amplifier ground area))
This was simple case.

But I do not understand why you now want pick up this old different issue to here - this new noise issue is enough complex without any extra mixing and shaking. 

Did you read what I have told about this new noise issue - my english is bad but I think this not now reason for misunderstooding?

Also other peoples have explained this case very well.

Just ago I explain (agen, just for you) where is this problem now... 

And now agen: Problem is in Adapter board  SMPS circuits and  PSU board SMPS circuits. AND they need repair - modify!

Owon have also made  changes  and new equipments from factory are now normal afaik. Also I have these normal units directly from factory.

[luca1000]

Owon have also made  changes  and new equipments from factory are now normal afaik. Also I have these normal units directly from factory.

If possible, can you do a statistic about the last 2 months how many units are "normal" and how many still have the problem ?

If I have understand there are some improvement by owon.

Sometimes on the forums there are informations not updated.

I suppose the new "defected" units can be "better" then the previous "defected" unit ?

If possible, can you attach some screenshots of a new factory (last release) "Normal" and "defected" unit.

I like to known in what measure a new "defected" unit differ by a new "Normal" units.

[luca1000]

I was find myself the response ( I think):

http://owon.forumup.com/viewtopic.php?t=177&mforum=owon

The difference is huge !!!

I like to know how many are defected (in percent if possible).

[lemon]

If "lemon" show this last image so that mains power is disconnected and scope run using battery, situation and noise is different.

I must suppose yes, otherwise what type of test is this ?? Don't have sense ...

I' am curious about this.

Unfortunately, mine situation is different from what we are expected!
With well charged battery from the worst to best the sequence is: battery (?400mV), battery+ac main(?300mV), ac main (?150mV) - Cheked by Owon Probe after Self Cal procedure and Probe adjustment.

[lemon]

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!

[rf-loop]

Unfortunately, mine situation is different from what we are expected!
With well charged battery from the worst to best the sequence is: battery (?400mV), battery+ac main(?300mV), ac main (?150mV) - Cheked by Owon Probe after Self Cal procedure and Probe adjustment.

Yes, this is unexpected result.
I have seen before:
(a) battery+ac  most bad, 
(b) ac without installed battery (battery out) less than  a 
(c) with battery alone without ac connected,  less than  b

It need some more investigation. I have some small suspects but too early to say.

[luca1000]

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 ??

[lemon]

Unfortunately, mine situation is different from what we are expected!
With well charged battery from the worst to best the sequence is: battery (?400mV), battery+ac main(?300mV), ac main (?150mV) - Cheked by Owon Probe after Self Cal procedure and Probe adjustment.

Yes, this is unexpected result.
I have seen before:
(a) battery+ac  most bad, 
(b) ac without installed battery (battery out) less than  a 
(c) with battery alone without ac connected,  less than  b

It need some more investigation. I have some small suspects but too early to say.

Yeap, it is very strange and I have no the knowledge to explain it.
You have my revisions of boards (p.m at yours forum)...