VOLTCRAFT DOV series

[Martin72]

Another note on the ripple at 200 mV/10 V...
As mentioned, this only happens when a specific relay switches.
So the path must be carrying this ripple—or rather, this interference.
I was able to trace the path back a little, but at a certain point it goes “down,” and I can't get to it while the unit is running.
A schematic for this section would be a godsend; I was in touch with Owon, but I think once they realized I had a Voltcraft, they went completely silent.
(Which is a common issue with Chinese manufacturers—99% of the time, their support staff are people who don't know anything about the product because they work in sales.)
Be that as it may, I'm going to continue anyway...
Why? Because it appeals to me—I don't actually need the scope at all.
But the thrill of finding and fixing it...
Right now, I’m trying to figure out where the GND switching kicks in.
If you set the coupling to GND in the channel menu, everything goes flat.
So where exactly does it switch to GND? That would help narrow down the search area.
We’ll see...

[Olex]

Hi everyone!
I'm a newbie on the forum, recently bought this oscilloscope, and am following the topic with interest.
It seems to me that the ground reference is implemented via software.

[Martin72]

Hi Olex and welcome..

GND switching simply has to be handled by the software.
The only question is where in the signal path the GND connection is made.
At least I found the switch for AC coupling; the optocouplers are connected more or less directly to the BNC inputs.

recently bought this oscilloscope

And it haves the same problem, right?

[Olex]

Hi Olex and welcome..

Thanks!

At least I found the switch for AC coupling; the optocouplers are connected more or less directly to the BNC inputs.

I have a feeling that this is completely software-based, without any physical grounding of the output.

And it haves the same problem, right?

Yep, same exact crap.
I even compared the board with the Owon mentioned earlier in the thread and couldn't find any difference.

[Martin72]

Of course, that’s a possibility—which would be a bit of a shame from the perspective of someone trying to troubleshoot the issue.
But I also don’t want to rule out the possibility—at least not anymore—that I’m chasing a phantom when it comes to the hardware.

[Aldo22]

I have a feeling that this is completely software-based, without any physical grounding of the output.

I think so too.
A reading of exactly 0.000pV doesn't seem plausible to me.
The Hantek still shows significant readings in GND coupling, which suggests that it's actually physically grounded.

[Martin72]

I briefly considered trying the Owon firmware, but there's nothing in the Owon database.
To be more precise, there isn't a single firmware file available for any Owon oscilloscope, no matter how old it is.

[Microcheap]

If you don't mind to try, I got a firmware update file from Owon. It works for the ADS800A and ADS900A with FW older than V1.0.1.0.17, I don't know about the Voltcraft but it should be the same.

Just copy the ota_update.zip to a memory stick (FAT32), plug it to the scope and open the App Center, it will show an update confirmation.

I've already tried it and it makes no difference regarding the ripple issue though.

I didn't test it further yet but one noticeable difference is regarding the cooling fan. Before, when the fan was spinning at low speeds it would make a very annoying whining noise, now it is fully on or off, no more speed control and the sound is louder.

[Aldo22]

If you don't mind to try, I got a firmware update file from Owon. It works for the ADS800A and ADS900A with FW older than V1.0.1.0.17, I don't know about the Voltcraft but it should be the same.

Just copy the ota_update.zip to a memory stick (FAT32), plug it to the scope and open the App Center, it will show an update confirmation.

I've already tried it and it makes no difference regarding the ripple issue though.

I didn't test it further yet but one noticeable difference is regarding the cooling fan. Before, when the fan was spinning at low speeds it would make a very annoying whining noise, now it is fully on or off, no more speed control and the sound is louder.

Thanks for the download. 

What I don't quite understand: Do you have both the Owon and the Voltcraft?
If so, why do you say “I don't know about the Voltcraft but it should be the same."?
If not, does the Owon have the same ripple problem, or how do you know it doesn't help?

[Martin72]

Hi,

First of all, the update itself went smoothly; my Voltcraft now has a 17 instead of a 14 at the end of the version number.
So it’s not “name-specific,” which is great.
Unfortunately, it didn’t help; the ripple is still there.

[Aldo22]

First of all, the update itself went smoothly; my Voltcraft now has a 17 instead of a 14 at the end of the version number.
So it’s not “name-specific,” which is great.
Unfortunately, it didn’t help; the ripple is still there.

Thanks for being the guinea pig!   

I was afraid it wouldn't work because I had taken a quick look at “ota_misc.json” and only the ADS models are listed there.

{
    “int_models”: [
        { “int_model”: “ADS802A”, ‘version’:" V1.0.1.0.17" },
        { “int_model”: “ADS804A”, ‘version’:“V1.0.1.0.17” },
        { “int_model”: “ADS812A”, ‘version’:“V1.0.1.0.17” },
        { “int_model”: “ADS814A”, ‘version’:“V1.0.1.0.17” },
        { “int_model”: “ADS822A”, ‘version’:“V1.0.1.0.17” },
        { “int_model”: “ADS824A”, ‘version’:“V1.0.1.0.17” },
        { “int_model”: “CEI914”,  ‘version’:“V1.0.1.0.17” },
        { “int_model”: “CEI924”,  ‘version’:“V1.0.1.0.17” },
        { “int_model”: “ADS912A”, ‘version’:“V1.0.1.0.17” },
        { “int_model”: “ADS914A”, ‘version’:" V1.0.1.0.17" },
        { “int_model”: “ADS922A”, ‘version’:“V1.0.1.0.17” },
        { “int_model”: “ADS924A”, ‘version’:“V1.0.1.0.17” }
    ]
}

Would you recommend this update?
What do you think of the change to the fan control?

Do you know a way of saving the original FW? Or is there a factory reset proc.?

[Martin72]

Hi,

I just installed the update myself, but generally speaking, you should keep your devices up to date because updates can include many unspecified improvements.
Well, in this case, everything is under wraps as far as documented changes go—or did you receive a revision history with the update, @Microcheap?

What do you think of the change to the fan control?

You can't really achieve any kind of thermal stability with those thin pieces of sheet metal anyway, so I, at least, don't have a problem with the fan control ultimately just being on or off.

Do you know a way of saving the original FW? Or is there a factory reset proc.?

No, I didn't see anything like that when I updated either.
By the way, I think the (compressed!) file size is huge for a simple update.

[Aldo22]

Thanks!

By the way, I think the (compressed!) file size is huge for a simple update.

This is probably not a patch, but rather a replacement of the entire system.
See the attachment.


Btw: Did the splash screen change to "OWON" instead of "Voltcraft"?

[Martin72]

Not much—if anything at all—has changed in that regard, at least as far as obvious changes go.
Well, the fan control—that stands out.

[Martin72]

Btw: Did the splash screen change to "OWON" instead of "Voltcraft"?

No...
I could have sworn I had version 14 before...
Unfortunately, I only have a version screenshot from my first DOV704, and it said 13, hmm...
Anyway, a bit about the fan “control”:
After booting up, once the scope is ready, the fan is initially turned off.
It’s hard to tell if there’s some kind of temperature control logic behind this, because after 4 minutes the fan turns on—and doesn’t turn off again after that.
At least not after 10 minutes; I was sitting right next to it the whole time.

[Aldo22]

I could have sworn I had version 14 before...
Unfortunately, I only have a version screenshot from my first DOV704, and it said 13, hmm...

I have version 1.0.1.0.14.

Is there actually enough space to attach proper heat sinks to the “thin pieces of sheet metal”?
Would that help?

[Martin72]

So I wasn't dreaming after all—thanks.
Sure, you could still attach a heat sink, but given the peak temperatures we measured, it’s not really necessary.
If the fan continues to run constantly once it’s been turned on, the offset will also remain constant.
No, I wouldn’t do that right now.
But a better fan—that is, a quieter one—would be an option.

[Martin72]

I measured the rise time again, just in case the update might have changed anything, but no, it’s still the same—2 ns is just good.
Then I took another look at the decoders.
SPI
I couldn't get it to work at all—neither 2-channel nor 4-channel mode; nothing is displayed.

I²C, UART
Works as expected

CAN, LIN
At first I thought, “Oh no, that can't be right,” but then I saw the correct data in the table after all.
It would be great if Owon wouldn't put a “0” in front of every letter....Thanks.

Unpleasant:
After a certain base time, the scope simply stops decoding.
With other devices, the data table just gets longer when you do that, but with the Owon/Voltcraft, it just stops—completely.
Even if you pause and then zoom in, nothing is there anymore.
Strange thing.

Edit under construction

[Aldo22]

SPI
I couldn't get it to work at all—neither 2-channel nor 4-channel mode; nothing is displayed.

I'm not sure if you're aware of this:
Decoding starts with the trigger!
First, select the trigger type from the trigger menu and fill in all the fields, then click “Copy Trig” in the decoding menu.
I'm not sure if that will solve the problem, but you could give it a try.

[Martin72]

I'd be happy to do that, but it's usually not necessary—in fact, this would be the first scope I've ever had that requires this kind of procedure.
But I'll give it a try.

[tautech]

SPI
I couldn't get it to work at all—neither 2-channel nor 4-channel mode; nothing is displayed.

I'm not sure if you're aware of this:
Decoding starts with the trigger!

LOL



Martin well knows what he's doing and his trigger setting on the CKL channel and a rising edge for Idle Low would decode SPI on all ther DSO's in his possession.

Other settings in the Decode menu will be responsible for failure to decode or this DSO won't without using a decode trigger

[Martin72]

But Rob, you always have to be prepared for the unexpected, and that goes for this situation too...
It doesn't really make sense to set the SPI decoder to decode that way, but Aldo22 is right—with this scope, you have to set the trigger first and then, for some reason, copy its settings; otherwise, you won't see anything.
But that must be a bug, because at first you only see something in the table; if you zoom out, nothing is displayed on the screen (probably because the data packet is displayed somewhere between the clock and the data), plus the trigger doesn’t actually trigger at all—everything jumps around wildly—and for whatever reason, four trigger levels are displayed on the left...
There's definitely room for improvement in the software, no question about it.

[Aldo22]

plus the trigger doesn’t actually trigger at all—everything jumps around wildly—and for whatever reason, four trigger levels are displayed on the left...
There's definitely room for improvement in the software, no question about it.

Trigger Mode "Auto" or "Normal"?

[Martin72]

The only time it stays stable is when you press “Stop.” 
(“Single” doesn't trigger it)

And I just had my first freeze with this Scope...
That can and does happen; I just thought it was worth mentioning because the picture that followed—the one with the beetle—had me in stitches.

[tautech]

But Rob, you always have to be prepared for the unexpected, and that goes for this situation too...
It doesn't really make sense to set the SPI decoder to decode that way, but Aldo22 is right—with this scope, you have to set the trigger first and then, for some reason, copy its settings; otherwise, you won't see anything.
But that must be a bug, because at first you only see something in the table; if you zoom out, nothing is displayed on the screen (probably because the data packet is displayed somewhere between the clock and the data), plus the trigger doesn’t actually trigger at all—everything jumps around wildly—and for whatever reason, four trigger levels are displayed on the left...
There's definitely room for improvement in the software, no question about it.

I can do that on a DSO too. 

For simple decode triggering you must use trigger Holdoff to prevent retriggering within a packet.
Simple stuff Martin.