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

[akis]

I have already contacted the dealer asking for one of these new boards/adapters/whatever and they asked me to send them my serial number SDS71021211675 and also they asked me to attach a picture with the problem, so I sent them the one I posted here plus rf-loop's instructions.

I do not want to open the scope just yet in case they decide to take the scope back and replace it with a new one. I presume the new models have very little noise, yes?

If it comes to repairing, I presume the Owon "kit" is better than trying to hack into the scope?

[AndrejaKo]

In my experience, it's easier to just press the top power button and then carefully remove the back cover so that it slides over the button. I agree with trying to use warranty for this, if possible!

Insist on getting a scope from 2013. They should be much better than the 2012 version. Also on my scope, the main board had problems with turning on. Sometimes, it would freeze during boot. It could be that this is a bad batch.

[Carrington]

"Owon have extremely low noise  front end. There is available lot of tests about it. Even with these "noisy GND" versions."

My original text:

It need also here remember that IF signal is clean in oscilloscope BNC input there have not been any noise issue related to this "noisy GND" issue.
Owon have extremely low noise  front end. There is available lot of tests about it. Even with these "noisy GND" versions.

And I can stay behind these my word.

Are you trying to see that I am doing something wrong? What do you mean by "if signal is clean ..." ? Are you saying that I am doing something to pollute the signal? If yes then please please show me how to "unpollute" it. I only want it to work after all

No, it was lightweight note to carrington about how to quote.

Sorry if I bothered you, not my intention, but don't worry, hereafter I don't omit anything. 

[lemon]

I have already contacted the dealer asking for one of these new boards/adapters/whatever and they asked me to send them my serial number SDS71021211675 and also they asked me to attach a picture with the problem, so I sent them the one I posted here plus rf-loop's instructions.

I do not want to open the scope just yet in case they decide to take the scope back and replace it with a new one. I presume the new models have very little noise, yes?

If it comes to repairing, I presume the Owon "kit" is better than trying to hack into the scope?

This is the best that I wish to you!
The new versions are free from this noise_ground. Some members with new versions have measured a range of 25-40mV (10X) with full bundwidth.
The repairing with diy approach has its magic story but if you want a quickly and sure result, the psu and adapter change is must! Some dealers have start to coverage this issue by the warranty.

[akis]

So all this bullshit is because they used switched mode or buck converters which create tons of noise inside the scope? Could they not use some sort of linear technique (without the heat of course) ?

[AndrejaKo]

Does anyone have old Owon Labview operation examples file? There used to be one on old Owon site, but now the link leads to SCPI instructions

[Carrington]

Does anyone have old Owon Labview operation examples file? There used to be one on old Owon site, but now the link leads to SCPI instructions

[TomC]

Some pictures of the fixture I built to test the Owon PSU boards. The base was built from an old ATX PSU from which I retained the power SW, the AC connector and the fan. Inside the ATX PSU box there is a 5 ohm 100W resistor that along with the fan is used as the load for the 8.4V supply.

The first image shows the connectors. The power connector has an easy way to open the white wire to connect an ammeter. The battery connector is hooked up to two 4 ohm 25W resistors in series to provide an 8 ohm load that simulates charging the battery. There is also a 10 ohm 25W resistors with alligator clips that can be easily hooked up in parallel to the 8 ohm load. This will only be used to test the PSU's ability to switch to current mode when the output current reaches 3.75A. The connector that takes the place of the adapter board hooks up the switched 8.4V to the 5 ohm resistor inside, and the -7.6V to a 50 ohm 10W resistor on the back. It also connects the appropriate outputs to a green and a red LED. The AC trigger output is also connected to the terminal strip on back and easily available for scoping if necessary.

The second image shows the Owon PSU board installed in the stationary position. In this case, the ATX PSU case simulates the Z-plate for a more realistic environment when testing for common mode noise. In this image the 10 ohm 25W resistor is shown hooked up in parallel to the 8 ohm resistor.

The third image shows the Owon PSU installed in the movable position. This will be used when access to the printed circuit side is needed. In this image the white power wire has been opened and the ammeter is shown connected between the two ends. Because of the nature of PWM supplies, accurate current measurements can only be obtained with a true RMS instrument.

The fourth image shows the components mounted on the back of the ATX PSU.

[lemon]

I see that your project goes well and very soon we have your first observation about this.

Simple and smart construction, bravo TomC 

[AndrejaKo]

@Carrington: Thanks a lot!

@TomC
Great construction!

[lemon]

So all this bullshit is because they used switched mode or buck converters which create tons of noise inside the scope? Could they not use some sort of linear technique (without the heat of course) ?

I don't know if they used switched mode psu because is less expensive or they want to avoid more temperature inside the scope, it has tight internal either.
Also, I don't know what do the others companies about this, but finally the major problem (for my opinion) wasn't the switched mode but the bad design. Today with the same internal topology inside (psu+adapter boards) the ground noise is low and acceptable.

[TomC]

Does anyone have old Owon Labview operation examples file? There used to be one on old Owon site, but now the link leads to SCPI instructions

This seems to be still available but in a different place. Go to technical data and then click Application.

[TomC]

Haven't been able to find a reliable, repetitive way to measure noise using the PSU test fixture. I'm thinking perhaps an LISN similar to the ones used to certify for EMI may help. May try to build one tomorrow.

[lemon]

TomC noise varies each time to measure it? LISN could to be help you, as you says.

I found another link, here in the eevblog about SDS7102 that have some interesting information. The link is https://www.eevblog.com/forum/reviews/owon-sds7102-i-don%27t-believe-it!/.

I summarized this thread to:
1) someone improved the noise spikes, just a very well cleaning of the mainboard and mainkeybord boards (many fingerprints on that). I think mine these boards have also many of these fingerprints.
2) there is a talk about what is language of fw - they conclused that is building on OSGi framework (java).
3) there is a suggested mod to psu fom less battery draining but I don't understanding the solution (TomC, please look that)

[AndrejaKo]

Does anyone have old Owon Labview operation examples file? There used to be one on old Owon site, but now the link leads to SCPI instructions

This seems to be still available but in a different place. Go to technical data and then click Application.

It's not there. The link which says it's the LabView file actually leads to SCPI file.

@lemon

I read that thread and after reading it carefully inspected my scope. The rotary encoder side of the main keyboard PCB was very clean on my scope, but its back side was dirty. There was some contamination of the main PCB as well and lots of it under the RF cans! I cleaned that up, but on my unit, it produced no visible results. On the other hand, it could be that my unit is too noisy for the results to be visible.


Also can someone here please try to access scope via network while the PC is wirelessly connected to the LAN? There are some issues discovered in the thread about Ethernet problems for Owon and I'd like to confirm if this is a bug somewhere or not.

[akis]

There is certainly an issue with the ethernet port which I will summarise here:
1) can ping over wireless but cannot download anything
2) cannot ping over homeplug devices, even though the Owon is connected straight to the router/hub
3) can ping and download only when the software is running on a PC which is directly connected to the LAN, ie no wireless and no homeplug

Number (2) maybe be a hint: when I connect my PC to the LAN through the homeplug device (the system using the electrical cables), it cannot ping or "see" the Owon - but just the Owon. I can ping and connect and use everything else in the house, including other PCs, TVs, Blue-Ray players, routers, wireless access points, printers, everything.

Observing how the oscilloscope software works, I have made another assumption :  it may be that in the handshake/start/stop download, they have used simple "waits" rather than proper synchronisation protocols, and these "waits" work only when you are on a real ethernet cable with specific latency. But when you are over the wireless / homeplug, there is added latency that probably throws all those primitive "waits" off. Just an idea.

[TomC]

TomC noise varies each time to measure it? LISN could to be help you, as you says.

The problem, I think, is that it's difficult to differentiate between conductive and radiated noise using the method of the long ground lead and the probe both connected to a common ground. I think this is further compounded by the open air environment. So the noise is different at different locations and also depends on the position of the ground lead and probe in respect to other components, connecting wires, etc. This will make it difficult to determine if a mod actually gives better results or not.

3) there is a suggested mod to psu fom less battery draining but I don't understanding the solution (TomC, please look that)

I looked at the mod from muvideo, his comments are based on the PSU schematic in the Service Manual. He is proposing adding additional components that may be difficult to fit on the existing PSU board, but the idea seems sound otherwise. In my opinion, if battery drainage is a problem, a simpler to implement idea would be what rf-loop suggested, trying to find a substitute Standby switch which is DPST instead of SPST. This way you could use the extra switch to disconnect the battery.

If I had the battery option I probably wouldn't have this problem because I leave the scope on Standby all the time.

[lemon]

You've right, if you can't to stabilize the variables you can't to determine if a mod actually gives better results or not. But I am sure something solution you'll find.

I looked the thread again and at the last message he says that have battery drainage (1/2) after two months. He had used an extra switch to positive before.
Finaly, I don't know if this mod is usefull becouse the Lipo battery has a drainage itself.

[TomC]

Also can someone here please try to access scope via network while the PC is wirelessly connected to the LAN? There are some issues discovered in the thread about Ethernet problems for Owon and I'd like to confirm if this is a bug somewhere or not.

I tried it wirelessly from the laptop. It works as well as from the PC with a wired connection, which is not that great anyway. It's slow, freezes the scope if you do High Memory Depth with the Acquire length set to 10M, and the SCPI command line emits an error and freezes the scope. Other than that it limps along.

By the way, where is that thread at, I tried a search but came out empty.

[AndrejaKo]

Also can someone here please try to access scope via network while the PC is wirelessly connected to the LAN? There are some issues discovered in the thread about Ethernet problems for Owon and I'd like to confirm if this is a bug somewhere or not.

I tried it wirelessly from the laptop. It works as well as from the PC with a wired connection, which is not that great anyway. It's slow, freezes the scope if you do High Memory Depth with the Acquire length set to 10M, and the SCPI command line emits an error and freezes the scope. Other than that it limps along.

By the way, where is that thread at, I tried a search but came out empty.

Here's the link https://www.eevblog.com/forum/testgear/owon-sds7102v-ethernet-port/
My scope doesn't seem to respond to ARP at all, based on some tests I did. I'm in a bit of rush at the moment, but I'll do some more serious packet capturing next week and try to get to the bottom of this. I'm not sure how the scope works at all, if it's refusing to talk ARP.

I'm not sure what OS you're using, but on most popular ones, you can type arp -a in terminal and it should show ARP cache. Could you please try doing some work with the scope over network and report if its IP address shows up in ARP cache after working with it?

[TomC]

My scope doesn't seem to respond to ARP at all, based on some tests I did. I'm in a bit of rush at the moment, but I'll do some more serious packet capturing next week and try to get to the bottom of this. I'm not sure how the scope works at all, if it's refusing to talk ARP.

I'm not sure what OS you're using, but on most popular ones, you can type arp -a in terminal and it should show ARP cache. Could you please try doing some work with the scope over network and report if its IP address shows up in ARP cache after working with it?

It's in the ARP cache. I tried this from the laptop through wireless to a Netgear router. While I was experimenting with this the wireless got knockout and I had to reboot the router. May be a coincidence that this happened while communicating with the Owon, but this doesn't happen often during regular use. Then again, I seldom use the LAN option to communicate with the Owon. The images show the Lan port settings on the Owon and the results of the test. The first Arp was done before communicating with the Owon.

[lemon]

As we know, at the front of SDS case series there is an infrared "eye" but we haven't any information about this.
Finally it seems that this is an option that Owon never development or let it be as is.

If you look carefully the attachment photo from the "L" keyboard, it seems that there is the routing and position of an IrDA, with extra positions for the appropriate resistors and capacitor. This ends at the joined pins to main keyboard.

I don't know if the rest of main keyboard is ready for that (I see some IC's like 8-ch multi/demultiplexer and one dual binary counter), the mod it seems easy but the fw doesn't support this.

[Hydrawerk]

Well, (infrared) remote controlled oscilloscope is a good idea. More useful than a touch screen. At LeCroy they use a detachable keyboard...
https://www.eevblog.com/forum/testgear/the-most-weird-and-funny-dso-metrix-mtx3000/msg221681/#msg221681

[akis]

Is there anything in the Owon at 150KHz? I was trying to work on a linear DC charger I am building, and saw this sawtooth curve at 150KHz - I could not understand where it was coming from.

[lemon]

Mine is with low gnd_noise and I don't see anything at 150KHz (full or limited BW)

The fft_150KHz = is without any probes on scope, it is clear.
The fft_150KHz_with probe = with a probe on channel 1 to the air.