Author Topic: OWON VDS1022I Quick Teardown (versus the Hantek 6022be)  (Read 120909 times)

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Offline Gyro

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Re: OWON VDS1022I Quick Teardown (versus the Hantek 6022be)
« Reply #500 on: December 03, 2019, 01:41:44 pm »
Good first interpretation.

Looking at my unit, the AD9288 RREFinA and REFinB are tied to REFout (pins 5,7,6), that makes sense as it's the most accurate reference source available.

With those two references fixed, I think that all three programmable values relate to the two AD603s. Checking around the AD603s, Pin 2 (GNEG - negative voltage increases gain) on both channels are linked together and decoupled to ground - these must be connected to a bias network somewhere (I didn't fully trace it out) and so I don't think they are involved in calibrations (there is no common cal setting for both channels).

Pin 1 (GPOS - positive voltage increases gain) of each AD603 is connect to an RC network, which in turn is fed by one half of an SGM8292 dual high voltage rail to rail opamp, on my unit, on the back of the board, near the ARM CPU. These form gain networks which are then driven by PB0.5 and PB0.7 port pins on the CPU. I Suspect that these are controlling the AD603 gain pin levels using PWM (the alternate functions listed on PB0.5 and .7 list ADC but not DAC).

I think this brings us back to the Firmware controlling gain and, zero and offset via those two pins, doing the appropriate compensations in code. Coarse Gain is fairly self-evident. I suspect that Zero Amplitude and Zero Compensation work together, to give both zero, and equal measurements / deflection for equal positive and negative voltages.

That's my best guess anyway.

(My earlier thoughts about Zero Compensation compensating opamp offsets is probably wrong - they would only be relevant at low signal levels (Zero Compensation exists on all ranges) and would be automatically included anyway in the the Zero adjustments provided).

Other interpretations very welcome!


P.S. I noticed in the AD9288 datasheet that a 10 bit pin compatible upgrade is available. That could be fun if we had full control of the Firmware and FPGA code. :) Alas...
« Last Edit: December 03, 2019, 02:00:32 pm by Gyro »
Chris

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Offline camomille

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Re: OWON VDS1022I Quick Teardown (versus the Hantek 6022be)
« Reply #501 on: December 03, 2019, 02:55:07 pm »
I will analyze your deduction, in this area you are much faster than me, I started to make the schema on paper around the AD603.
I made a discovery, the circuit "8061" (AD8061 / 8063) can isolate each channel by pin 5.
FPGA is just a logical matrix, but to decode it is another story.
 

Offline camomille

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Re: OWON VDS1022I Quick Teardown (versus the Hantek 6022be)
« Reply #502 on: December 03, 2019, 04:00:09 pm »
For me, it is the outputs of the 2 DAC (IDAC0 / IDAC1) that go to SGM8272, respectively PB0.10 pin 47 and PB0.11 pin 48 of the 64 Pin TQFP SIM3U1xx .
« Last Edit: December 03, 2019, 06:33:29 pm by camomille »
 

Offline Gyro

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Re: OWON VDS1022I Quick Teardown (versus the Hantek 6022be)
« Reply #503 on: December 03, 2019, 06:30:09 pm »
 :palm: Doh, yes, of course, you're right - I was looking at the 80QFN datasheet footprint, I was too busy balancing the board vertically while probing both sides!  Yes, IDAC0/1 it is then. It makes a lot more more sense than PWM.

I have to take the screws out again later to check the AD8061s. According to my old photo they are indeed marked 8061 and according to the datasheet, only the 8063 has the disable pin.

I am still wondering the about the 'mechanics' of the 'Self Cal' operation. Whether it is an offset cancellation (I think what Tek call 'signal path compensation') or whether it is gain too. I suspect that some of the secrets are hidden under the shield.
Chris

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Offline camomille

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Re: OWON VDS1022I Quick Teardown (versus the Hantek 6022be)
« Reply #504 on: December 03, 2019, 06:36:45 pm »
But you too are right because there is a second SGM8272 underneath and he is attacked by logical outputs.
I just changed the image above.

it is good 8061 but surely a manufacturer with the box of 8063
« Last Edit: December 03, 2019, 06:41:54 pm by camomille »
 

Offline Gyro

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Re: OWON VDS1022I Quick Teardown (versus the Hantek 6022be)
« Reply #505 on: December 03, 2019, 07:40:18 pm »
Ah, good - it's always nice to be a little bit right.

The AD8061s are definitely 8061 on my board revision - SOT23-5 pin package, not SOT23-6 (8063), so lacking enable.

I'd never paid any attention to the SGM8272 on the top side, from its position I think I assumed that it was PSU related. Following the outputs leads me to the two LMH6551 differential output opamps which are the stages between the AD603s and the AD9288 ADC. On my board they go to a large tacked-on Tantalum decoupling capacitor before going to the bias network on the LMH6551 Pin 1 (input -). This looks to be in non-inverting configuration, so it must be an offset adjustment for the LMH6551. [EDIT: Vcm (common mode input) of the LMH6551s are driven from the ADC Vref Out, as Fig. 33 in the datasheet (Driving an ADC)]

I suppose this makes sense because by the time the signal has reached the LMH6551 it has already been scaled to a fixed range by the AD603, input attenuator relays etc. so will work as a range independent offset adjustment going into the ADC (but still adjustable on a range by range basis).

Ok, so now we have the Coarse gain adjustment (PWM?) driven into the AD603s from PB0.0 / PB0.2 via the bottom SGM and offset adjustment at the LMH6551s driven from PB0.10 / PB0.11 (10 bit IDAC?) via the top SGM. It's making sense.

EDIT: The picture of my board revision (from Reply #12), showing the tacked-on Tants...



P.S. I suspect that your board doesn't have the U29 footprint - an interesting evolutionary relic!
« Last Edit: December 03, 2019, 08:56:40 pm by Gyro »
Chris

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Offline Gyro

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Re: OWON VDS1022I Quick Teardown (versus the Hantek 6022be)
« Reply #506 on: December 03, 2019, 08:10:46 pm »
One more thought... The s/w will normally expect the ADC exactly half scale code to be Analogue zero. I wonder if a change in what it expects here could be regarded as a 'Zero Amplitude' adjustment?

EDIT: No, too many digits. I was forgetting it's only 8 bits.
« Last Edit: December 03, 2019, 10:22:02 pm by Gyro »
Chris

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Offline camomille

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Re: OWON VDS1022I Quick Teardown (versus the Hantek 6022be)
« Reply #507 on: December 04, 2019, 06:51:58 am »
Just a small precision before attacking the day, the DACs are 10 bits current output (0.5, 1, 2 ma) .
The circuits marked "YJAA" are SGM2019A.
« Last Edit: December 04, 2019, 09:30:25 am by camomille »
 

Offline Gyro

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Re: OWON VDS1022I Quick Teardown (versus the Hantek 6022be)
« Reply #508 on: December 04, 2019, 01:16:59 pm »
Yes, lots of nice local regulation on the analogue supplies.

I've just been doing some quick measurements and found that both Zero Amplitude and Zero Compensation affect the IDAC outputs to the LMH6551s. I was hoping that it would be just one or the other.

As expected, the Coarse Gain adjustment changes the GPOS gain adjustment pins of the AD603s.


P.S. I still wonder how it performs the Self-Cal. Watching the screen, it seems to adjust  the zero positions of both traces at the centre of the screen, and then do the same again at some positive displacement on the screen. It could be that somewhere (under the screening can?) it switches in a positive reference, tapped of an analogue supply so that it can determine what offsets there are in the system.

Alternatively, it might be offsetting by changing the Zero Amplitude setting and then optimising the Zero Offset setting at two positions. I'm not sure why it would do this (apart from maybe optimising ADC linearity?). With a 10 bit IDAC it should be possible to set the zero offset of an 8 bit ADC quite closely.

I can't see any way of Self-Cal setting the Coarse Gain. It would either need a separate reference or feed back of the ADC ref. I think this is a manual cal only.
« Last Edit: December 04, 2019, 01:56:09 pm by Gyro »
Chris

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Offline camomille

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Re: OWON VDS1022I Quick Teardown (versus the Hantek 6022be)
« Reply #509 on: December 04, 2019, 02:38:55 pm »
You have a separate reference in SIM3U156 :

PB0.8 pin 49 VREFGROUND
PB0.9 pin 48 VREF
 

Offline Gyro

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Re: OWON VDS1022I Quick Teardown (versus the Hantek 6022be)
« Reply #510 on: December 04, 2019, 05:43:20 pm »
As far as I can see, the SIM3U156 VREF is used as a common mode reference node for the top side SGM8292, which is effectively being used as an I/V converter for the offset adjustments.

They've been careful to take the SGM8292 supply rails from the analogue regulators at the front of the board.

Actually, they may well be using the SIM3U156 VREF indirectly as a calibration source for the ADC... As it is the reference for the IDACs, they can feed a known offset voltage to the LMH6551s and read back the resulting ADC reading. That will allow closed loop calibration of the ADC (and LMH6551 offsets).

I can't see how they can go past that though (to the AD603 gain calibrations) other than to null their offsets by assuming 0V inputs (probes disconnected). There are relay clicks during self-cal, I don't know how many relays there are under the shield, but there must be at least two per channel, one for AC/DC coupling and one for the higher voltage ranges, maybe there's another shorting one.
« Last Edit: December 04, 2019, 05:53:05 pm by Gyro »
Chris

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Offline camomille

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Re: OWON VDS1022I Quick Teardown (versus the Hantek 6022be)
« Reply #511 on: December 04, 2019, 06:35:12 pm »
I think it's the same model (NEC) as in the 4 channels.
 

Offline Gyro

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Re: OWON VDS1022I Quick Teardown (versus the Hantek 6022be)
« Reply #512 on: December 04, 2019, 06:41:58 pm »
Ah, only one per channel on that one, presumably AC/DC coupling. It's not the same circuit as the VDS1022 though - it's missing the trimmer caps near the rear of the shields.

At some point, curiosity is going to persuade me to desolder the shield but I'm trying to resist!
Chris

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Offline camomille

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Re: OWON VDS1022I Quick Teardown (versus the Hantek 6022be)
« Reply #513 on: December 04, 2019, 07:03:38 pm »
Surely this model double coils latch.
 

Offline Gyro

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Re: OWON VDS1022I Quick Teardown (versus the Hantek 6022be)
« Reply #514 on: December 04, 2019, 07:12:12 pm »
Yes, it is a double pole changeover (DPDT), the two contacts are mechanically linked. It uses two coils (bistable) so is stable in both states. It minimises current draw and power dissipation. A good thing to do when USB powered.
Chris

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Offline camomille

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Re: OWON VDS1022I Quick Teardown (versus the Hantek 6022be)
« Reply #515 on: December 05, 2019, 12:23:20 pm »
My contribution to enlighten this subject
« Last Edit: December 05, 2019, 12:37:25 pm by camomille »
 
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Online indman

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Re: OWON VDS1022I Quick Teardown (versus the Hantek 6022be)
« Reply #516 on: December 05, 2019, 01:49:24 pm »
I noticed another problem in the mathematical channel that is present in all versions of the shell, including 1.0.30. The selected range value (for example,5V) is not saved when the program is reloaded. There is also no preservation of this meaning if you remove the bird from the function of mathematics and put it again.
Can you confirm or deny this problem?
 

Offline Gyro

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Re: OWON VDS1022I Quick Teardown (versus the Hantek 6022be)
« Reply #517 on: December 05, 2019, 05:49:31 pm »
My contribution to enlighten this subject

Nice reverse engineering, thanks.  :-+

I'm away from my unit for a few days.
Chris

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Online jemangedeslolos

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Re: OWON VDS1022I Quick Teardown (versus the Hantek 6022be)
« Reply #518 on: December 17, 2019, 08:50:54 pm »
Hello,

I bought a VDS3102 that I haven't received yet.
Do you know if the software is the same between the 1022 and the 3102 ?
I can't download the software from Owon, I don't know why.
It seems that most of their links are dead.

It is nice to be able to change the channel color. I will look more deeply when I received to scope.
 

Offline Gyro

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Re: OWON VDS1022I Quick Teardown (versus the Hantek 6022be)
« Reply #519 on: December 17, 2019, 09:30:15 pm »
I'm not sure why you're having trouble downloading the s/w, it's on their support page (I just tried it) ... https://www.owon.com.hk/support_PC_Software_list3

The best bet is normally to install the version that comes on the CD and then check if the site version is a later Rev.

No, the s/w is different between the two (although I'm sure they are closely related) - you can normally delve deeper by unzipping the installer exe file.


P.S. You can find the user manual in the support pages too.
« Last Edit: December 17, 2019, 09:43:24 pm by Gyro »
Chris

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Offline camomille

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Re: OWON VDS1022I Quick Teardown (versus the Hantek 6022be)
« Reply #520 on: December 18, 2019, 07:59:45 am »
A small gift for the Christmas holidays
« Last Edit: December 18, 2019, 08:02:14 am by camomille »
 

Offline Gyro

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Re: OWON VDS1022I Quick Teardown (versus the Hantek 6022be)
« Reply #521 on: December 18, 2019, 09:35:43 am »
Hey Camomille, that's very useful - thank you!  :-+

It's the sort of thing I kept meaning to do, wished I had, but never got around to! I wondered how they implemented things like the multi Input/output.

Now to work out why my earlier version PCB uses a switcher for the -2.5V rather than an LM337 - they must have had some reason for changing it.

I will try to get around to lifting the shield and taking some photos sometime over Christmas.
Chris

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Online jemangedeslolos

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Re: OWON VDS1022I Quick Teardown (versus the Hantek 6022be)
« Reply #522 on: December 18, 2019, 10:12:34 am »
It seems that I tried only when the links were dead  :palm:
It is working great now, thank you  :)

 

Offline camomille

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Re: OWON VDS1022I Quick Teardown (versus the Hantek 6022be)
« Reply #523 on: December 18, 2019, 10:14:30 am »
Hello Chris

It is between diagram and synoptics to understand the operation, I deliberately forgot the decoupling capacitors.
What I find interesting is the hc595 which serves as a serial / parallel interface between the cpu and the inputs (6 lines).
One might think that one of these lines isolates the inputs and authorizes a reference voltage for the auto calibration.
I also highlighted the FPGA series programming.
My model does not have circuits with a red cross.

Alain
 

Offline Gyro

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Re: OWON VDS1022I Quick Teardown (versus the Hantek 6022be)
« Reply #524 on: December 18, 2019, 11:32:05 am »
It seems that I tried only when the links were dead  :palm:
It is working great now, thank you  :)

Glad to hear it.  :)

Thinking overnight, there may not actually be many differences between the VDS1022 s/w and the 3102. After all, they both have the same user interface. Irrc, the 3102 uses USB2 High speed rather than full speed (the reason it doesn't have a galvanic isolation option) so there will be differences in the device driver etc, and of course the FPGA firmware file will be different.

You may want to download the latest VDS1022 and the latest VDS1032 s/w, unzip the installer exe files to two separate folder trees (7zip works) and look for commonalities.
Chris

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