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

[TomC]

I've been considering the DIY options available, including the cost of materials and risk of voiding the Owon's Warranty, to reduce the GND noise on my scope. Yesterday I decided that the best option for me was to order a new PSU board and a capacitor to modify the Converter board from Owon. For those interested in the details, I've posted below the e-mails leading to this decision as well as the purchase transaction.

The agent responding to my e-mails is the same agent that previously indicated that Owon ---- "have not plan and exact date to make change for it now, because it is not quite abnormal" ---- referring to the GND noise. The good news is that he now confirms that changes in the PSU & Converter boards at least reduce the noise.

For those of you that have been holding out for a resolution of the GND noise issue before making a purchase decision, Owon's response seems to confirm previous reports of an early June resolution to the GND noise issue. If you are still cautious, check the forum in the coming weeks, I plan to post noise images before and after exchanging/upgrading the boards in my scope. Hopefully you can use these images to help you decide if the noise level is good enough for you.

As for those of us that already own a scope with the GND noise issue, Owon's response offers an alternative to a DIY solution for US $50 + money transfer fees. This is not as good as the free exchange that many of us believe Owon should have offered, but to me, it's not a totally unreasonable price to pay to improve the usability of your scope.

The bad news, at least for me, is that my bank charged me a $45 fee for the money transfer. Maybe doing the transfer via Western Union is less expensive if you can make it work. I have an account with them but I couldn't get their Web site to give me the option to transfer funds to a Bank Account in China. Maybe I didn't try hard enough or should have called them before giving up, but I just got impatient and used my bank's money transfer service instead.

I plan to open my scope later today to get acquainted with the procedures I'll need to perform when the Owon shipment arrives. While I'm at it I'm going to try ferrite cores in the cable between the PSU and the converter board, as well as from the converter board to other scope components. I'll be posting the results as soon as I get done.


------------------------------------------------------------------------------------------------------------------
To: _____ (at Owon)

Subject: Re: GND Noise

Dear _____ or other Tech Support agent,

One of your customers reports that during a recent communication with Owon, one of your employees has indicated that the GND noise issue was resolved about three weeks ago. He also reported that Owon can supply the new boards (PSU & Adapter DC/DC) for about US $50. In an effort to resolve, or at least improve the GND noise on my unit, I would like to purchase these boards from you if they are indeed available. Please indicate the actual price and what needs to be done to complete this transaction.

Best regards,

------------------------------------------------------------------------------------------------------------------
To: _____ (TomC)

Subject: GND Noise
 
Hi _____,

Sorry for my mistake information, after consulting about if from our engineer, I found this GND noise has reduced much by replacing new board. But please note that the noise can’t be solved 100%, but reduced.

Only two spares need to be replaced, one is Power Supply Board and the other is a Capacitance in convert board.

The price include shipping cost to USA is USD50 totally. Please pay to our bank account. (paypal or credit card are not acceptable, but western union is preferable)

If you agree, please tell me your below information:

Your address
Consignee
Telephone number

Our bank account is
BANK INFO

\\\\\\\\\\\\\\\\\\\\\
||||||||||||||||||||| (I didn't post names or the bank information to protect privacy, but the bank information
|||||||||||||||||||||  provided contained everything I needed to transfer funds from my bank account to their bank
|||||||||||||||||||||  account)
\\\\\\\\\\\\\\\\\\\\\

You could make payment firstly.

Have a nice day

------------------------------------------------------------------------------------------------------------------

To: _____ (at Owon)

Subject: Re: GND Noise

Hi ______,
 
I just transferred USD50 to your bank account for the new boards. You should receive e-mail from my bank in my behalf shortly. My Address information is as follows:
 
\\\\\\\\\\\\\\\\\\\\\\\\\\
||||||||||||||||||||||||||
//////////////////////////
 
My telephone number is:

||||||||||||||||||||||||||

------------------------------------------------------------------------------------------------------------------
To: _______ (TomC)

Subject: Re: GND Noise

Hi ______,

We got your payment, thank you.
We will make shipment soon.
 
Attached is to show the capacitance I mentioned need to be replaced.

Have a nice day

[TomC]

While I had my scope open today, I installed some ferrites to see how much I could improve the GND noise.

The first picture shows the ferrites on the cables coming out of the converter board. The blue heat shrink on the left is covering a very small solid ferrite that I salvaged from discarded equipment. So all I can tell you about this one is that it is about .25" outside diameter and the inside diameter is just large enough to hold the two wires. The wires had to be pulled out off of the connector to install the ferrite. The ferrite on the small ribbon cable is a standard snap on small ferrite purchased at Radio Shack.

The second picture shows a medium size snap on ferrite on the ribbon cable between the PSU and the Converter board. This is also a standard ferrite purchased at Radio Shack. However, even this medium size ferrite is too large and doesn't allow the scope's cabinet to snap back together.

The third picture shows what I did to allow enough room for the cabinet to snap together. The ferrite halves can be easily removed from the snap on housing, and then held together with a cable tie.

The next 6 pictures show the GND noise before the ferrites were installed (first 3 pictures) and after the ferrites were installed and the scope was put back together (last 3 pictures).

Besides the improvement on the GND noise, I also found out that the amount of noise produced by placing the probe's cable next to the TFT panel was also greatly reduced from what I remember to have experienced in the past. I didn't think to get images before I installed the ferrites, so I'm only relying on memory for this last comment.

When I get the shipment from Owon, I plan to try the new board with and without ferrites, to see if it makes any kind of a difference.

[lemon]

Very well!
The noise is low without any peaks.

The member "rf-loop" had suggested a method for this.

Procedure for measurent of Noise GND
----------------------------------------------------
Make a Calibration procedure as the notes says (look in manual).
Compensate the probe as manual described.
Change switch probe to 10x.
Do the same and the Probe Owon Menu (10X).
Connect probe to Probe Comp and GND wire to GND. Fix the cable of probe like the attachment photo.
Turn CH2 off.
CH1 to DC, 50mV/Div.
Push Trigger 50%
Set the Acquire Length to 1M and the Mode to Peak
Set the Horizontal speed to 100us
Set the measurement to Voltage peak to peak (Vp to Owon) and write the value.

I updated my test process with your suggestion. 
Vp=34mV

Let me know if you would like me to try anything else.

You have very well noise level. Thanks for this information.
Now, there is no any problem to any low level signal for measurement.

You have the last improvement psu version of Owon.

[lemon]

@ TomC = Very informative all of this!

It is a pitty than Owon don't take money from Paypal or Credit Card.

As I can understand, the Owon has complete changed the psu board and makes only a capacitance change to adapter board.
TomC, they told you that the only change on adapter board is a capacitance to the specific area. Have you sent your s/n before about this or it is not related?

You have better results of noise level with the ferrites. You found a solution with the ribbon cable, very well!

With the new psu board, you 'll see if the ferrites will be usefull. We'll waiting for results.

[mlhstock]

I received my SDS7102V yesterday. I asked for the new version produced in June and the seller agreed, but they still sent me an old version (S/N is 1303xxx). The gnd noise is terrible, Vp-p is up to 160mV and lots of spikes. I asked for an exchange or refund and waiting for their answer.

[Nermash]

IMHO the best thing is to stop buying Owon all together, at least for 6 months untill the bad stock is sold or returned. I have SDS7102 from 2011, but now I wouldn't buy it, I would wait or buy something else.

[mlhstock]

I agree. It was a mistake to buy it now.

[Hydrawerk]

So never buy online. Buy a unit that you check for noise problems before.

[TomC]

TomC, they told you that the only change on adapter board is a capacitance to the specific area. Have you sent your s/n before about this or it is not related?

They have my serial number, but I don't now if this same mod applies to other serial numbers. The 1000pf SMD capacitor, where they show it, is directly underneath an electrolytic capacitor on the component side, so it's only bypassing it to help high frequency filtering. The adapter board in my scope looks exactly like the adapter board in the picture, except that it doesn't have the SMD capacitor.

[dgmoore78@yahoo.com]

I received my SDS7102V yesterday. I asked for the new version produced in June and the seller agreed, but they still sent me an old version (S/N is 1303xxx). The gnd noise is terrible, Vp-p is up to 160mV and lots of spikes. I asked for an exchange or refund and waiting for their answer.

I bought mine from a dealer on E-Bay (SMTZONE) that shipped the unit directly from Hong Kong.  Mine is from the new June batch and is very good.

[lemon]

TomC, they told you that the only change on adapter board is a capacitance to the specific area. Have you sent your s/n before about this or it is not related?

They have my serial number, but I don't now if this same mod applies to other serial numbers. The 1000pf SMD capacitor, where they show it, is directly underneath an electrolytic capacitor on the component side, so it's only bypassing it to help high frequency filtering. The adapter board in my scope looks exactly like the adapter board in the picture, except that it doesn't have the SMD capacitor.

When you received the new psu board, please give us some photos from up and down side.
Also, can you give us the adapter version that you have?

At the last, can you measure the noise with the bypassing (1000pF) only? Before, you installed the new psu board.

[AndrejaKo]

TomC, they told you that the only change on adapter board is a capacitance to the specific area. Have you sent your s/n before about this or it is not related?

They have my serial number, but I don't now if this same mod applies to other serial numbers. The 1000pf SMD capacitor, where they show it, is directly underneath an electrolytic capacitor on the component side, so it's only bypassing it to help high frequency filtering. The adapter board in my scope looks exactly like the adapter board in the picture, except that it doesn't have the SMD capacitor.

When you received the new psu board, please give us some photos from up and down side.
Also, can you give us the adapter version that you have?

At the last, can you measure the noise with the bypassing (1000pF) only? Before, you installed the new psu board.

+1 for that! It definitely looks like a simple modification that most of us will be able to do and looks easy to undo, should there be any warranty issues.

[rstoer]

TomC, they told you that the only change on adapter board is a capacitance to the specific area. Have you sent your s/n before about this or it is not related?

They have my serial number, but I don't now if this same mod applies to other serial numbers. The 1000pf SMD capacitor, where they show it, is directly underneath an electrolytic capacitor on the component side, so it's only bypassing it to help high frequency filtering. The adapter board in my scope looks exactly like the adapter board in the picture, except that it doesn't have the SMD capacitor.

Boy, you're really going all out to reduce a noise level I never thought was all that terrible. Your original figure was somewhat higher than my gen-one version but not nearly as bad as some. (Remember electroguy claimed 800mV !) With the ferrites you installed yours now measures slightly LOWER than mine, which is about 80mV under the same test conditions.
I actually tried installing ferrites on mine today but it there was no noticeable reduction. My boards are also different than most shown here (see photos). That was all I was willing to attempt as it's not a real-world issue. I never get that much noise when probing something. In fact just doing the 'standard noise test' with a short (spring) ground cuts the level by more than half.
Good luck with your modifications!

[AndrejaKo]

Just a quick question: Does the metal part of anyone else's top power switch get hot during operation? I noticed that mine does some time ago, but looking at the power board I couldn't find any obvious sources of heat that it could be dissipating. In the vicinity, there's a component in an isolated TO-220 package that's connected to the Z-plate and that's about it. Everything else seems cool when touched.

[lemon]

@ rstoer

You have an SDS7102 of 27th week of 2011. An older version that we have.
As your main psu board as adapter board are very different from newer models.
Yours results with 80/36mV are with a long/short ground cable. The 80mV initial noise level are very well.
Please look at post #1330 and repeat your test noise with these parametres (same conditions to all)
But I don't understand, there is no any improvement with ferrites in yours boards? IMHO only that two ribbon cables btw psu and adapter boar needs ferrites.
As your noise gnd level is lower as better you can measure low signals. Ground noise issue isn't Owon part, many other oscilloscopes have the same issues.

[lemon]

Just a quick question: Does the metal part of anyone else's top power switch get hot during operation? I noticed that mine does some time ago, but looking at the power board I couldn't find any obvious sources of heat that it could be dissipating. In the vicinity, there's a component in an isolated TO-220 package that's connected to the Z-plate and that's about it. Everything else seems cool when touched.

Andrejako, the top metal of power switch is connected to gnd of psu board (it doesn't needs, because it sends EMI like antenna, everywhere).
All the versions of psu boards are no identical. Some of these have a first mosfet (I think 5n60L) that really hots. If someone allumium heatshink connects with gnd of board...it hots all the gnd path!

[J4e8a16n]

Hi,


How do you save ch1 and ch2 at the same time?

How do you save ch1 ch2 and math or fft at the same time?


JP

[lemon]

Hi,


How do you save ch1 and ch2 at the same time?

How do you save ch1 ch2 and math or fft at the same time?


JP

Do you mean how to save in image file?
You can save the 2 channels or fft or maths in usb stick or via your computer and the Owon PC Oscilloscope software.

With at once 2 channels and fft you can't (I think) but there is a click option to Owon PC Oscilloscope software that you can see the channels or fft at the same image.

[tinhead]

can someone please export two specific csv's from an Owon?

one when Owon ch1 enabled, no signal connected, AC counpled, timebase set to 500us/DIV, 10Mpoint, 1GS/s and the first volt/div with no bw reduction, so i think 5mV/DIV. And then second one with same settings but ch1 set to gnd.

[J4e8a16n]

I meant ch1 ch2 on a usb key.

[lemon]

I meant ch1 ch2 on a usb key.

I haven't this time the oscilloscope in front of me.
From my memory, this saved is easy with Owon PC Oscilloscope Software.
I see now the pdf manual, at pages 49-50 described the "How to Save and Recall a Waveform"

[lemon]

can someone please export two specific csv's from an Owon?

one when Owon ch1 enabled, no signal connected, AC counpled, timebase set to 500us/DIV, 10Mpoint, 1GS/s and the first volt/div with no bw reduction, so i think 5mV/DIV. And then second one with same settings but ch1 set to gnd.

I am on summer holidays and I haven't the scope together.
I remember that saves direct in bin format but maybe the Owon Software can to save at csv,  otherwise some member will give you the bin file and you will convert to csv format with a converter.
At the first case, the 5mV/div will limit the BW probably, you must set to 10X the Probe Set to full BW.
At the second case, you probably want the "Ground Noise" (both the tip and ground clip to ground). For this we have follow the procedure that described to #1330 post.

Perhaps members like TomC or dgmoore78@yahoo.com can help you by csv or bin files.

[TomC]

When you received the new psu board, please give us some photos from up and down side.
Also, can you give us the adapter version that you have?

At the last, can you measure the noise with the bypassing (1000pF) only? Before, you installed the new psu board.

I got the tracking number from Owon and the package is already in the US, so it will probably be delivered by Saturday or Monday. I'll post pictures as well as the other information you want.

[TomC]

Boy, you're really going all out to reduce a noise level I never thought was all that terrible. Your original figure was somewhat higher than my gen-one version but not nearly as bad as some. (Remember electroguy claimed 800mV !) With the ferrites you installed yours now measures slightly LOWER than mine, which is about 80mV under the same test conditions.
I actually tried installing ferrites on mine today but it there was no noticeable reduction. My boards are also different than most shown here (see photos). That was all I was willing to attempt as it's not a real-world issue. I never get that much noise when probing something. In fact just doing the 'standard noise test' with a short (spring) ground cuts the level by more than half.
Good luck with your modifications!

What can I say, I'm retired, got to find something to do!

One thing I noticed on your scope is that the noise level using the short spring ground is more than twice the noise on the newer scopes. On mine the baseline noise (nothing connected to the BNC) is about 12mV, then, with the probe and short ground clip connected to the ground lug it increases by 2mV for a total of 14mV.

That makes me think that the signal path of scopes like yours was more polluted with noise than the newer scopes. That noise in the signal path is differential noise, different from the common ground noise that we are experiencing with the current GND noise issue. So it doesn't surprise me too much that the ferrites didn't make that much difference, because they only help with the common mode noise, and it seems you have very little to begin with, 80 - 36 = 44mV.

Since, you don't have any issues when probing signals, I imagine this includes low level signals, then, overall, I think your scope's usability is probably better than the newer ones. For scope's like ours, if you want to view and trigger on low level signals while using full bandwidth, you are forced to use a short spring ground.

The only other alternative is to limit the bandwidth to 20MHz or set the probe to X1 which limits the bandwidth to 6MHz.

[mlhstock]

Just wondering, how did it pass the EMI test?