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

[AndrejaKo]

I've noticed few interesting things in the manual.

 First, the scope doesn't need to warm up before self-calibration! I find that very interesting.

It's nice to see 50 ohm termination on the scope. No AC coupling with it though.

 M knob was renamed to G knob. Hopefully that will stop some whining about the knob name.

It's nice to see that they added the ability to see the main waveform when zoomed in. I didn't really miss that, since I often it was easier for me to zoom in by hand instead of going to menu and select zoom option. I would have liked it if they added a special zoom/unzoom button on the control panel.

I'm a bit disappointed that there are no options to adjust the HF and LF trigger filters. They would have been useful to me few times.

I like the fact that they managed to add the trigger frequency to the bottom panel, so it doesn't take up space from waveform window.

Also persistence can now be adjusted precisely up to 10 seconds.

It's great that they added the option to change file format for saved images!!! Also it seems that Copy button can now be used to save to flash drive as well. Is that possible on SDS series? I've seen some images that don't have save menu visible, but I'm not sure if they were made from the scope ore remotely. Directories can now be navigated as well. Firmware can be upgraded from a flesh drive now as well.

Apparently, it's now possible to see both FFT and the signal at the same time, judging by screenshots in the manual.

Unfortunately, it seems that now all measurements take up space on the waveform window. On SDS it's possible to have up to 4 measurements without taking up any area on the waveform window.

As far as the sampling is concerned, it seems that there are two ADCs. Scope can run in one, two or four channel mode and sample rate is halved in four channel mode. I'm not sure if it can run with 3 channels and I'm not sure which channels are active in 2 channel mode.

Manual doesn't seem to mention the dreaded "user-friendly voice warning" which was much bashed in the TDS thread.

[TomC]

I gave the manual a quick look and didn't see fine control for Vertical or Horizontal. Didn't see any differences on X-Y mode either. Can't really say I see a lot of improvement, just a few new features, like touch screen and 50 ohm input.

[Hydrawerk]

For me the new Owon TDS is bad scope that I would never buy. Who needs touch screen or voice output (??) when you have no built-in signal generator, decoding, or digital channels... 

[lemon]

AndrejaKo, you read it with a more attention than me.
Sure the choice btw 50 Ohm or 1MOhm input is fine but the only the AC operation with 50 Ohm is strange.
As TomC said, the fine function seems to be missing.
I looked at the Vertical Operation and I don't find something about it.
Also, I think that the XY function is improved but I don't read it with attention something like a quick tour.

I think, this fw is basic to ours SDS fw. It is not an other fw, is the same with some improvements and some extra capabilities that TDS Series have.

Hydrawerk, personally I don't agree with your statement.
It remindes me the flame btw Rigol and other brands. For me the capability of touch screen is a usefull capability for some quickly operations or entry text/numeric on filenames areas.
I don't understand why this function must be only with built-in signal generator or decoding.

[casinada]

TomC, what curve tracer do you have?
It looks interesting.

[AndrejaKo]

AndrejaKo, you read it with a more attention than me.
Sure the choice btw 50 Ohm or 1MOhm input is fine but the only the AC operation with 50 Ohm is strange.

Actually, it has only DC operation in 50 ohm mode. I wrote that it has no AC mode.

[TomC]

TomC, what curve tracer do you have?
It looks interesting.

Heathkit IT-3121. Bought it at eBay for $100 + $20 shipping

[Hydrawerk]

Hydrawerk, personally I don't agree with your statement.

Maybe one day I will try out this Owon TDS and I will find the touch screen useful, who knows.

[lemon]

I have almost 10mV improvement after some modifications to AOZ1094 circuit.

Here is the measurements that I had before.

The Average noise (16) at Acq. Mode is 22mV with 100us and 14-16mV with 500us (before 30-34mV)
The Sample (normal) noise at Acq. Mode is 32-40mV with the most to be btw 34-38mV (before 40-52mV).
The Peak noise at Acq. Mode is 32-44mV with the most to be btw 34-40mV (before 40-52mV).
 
The last attachment photo is what I do to adapter board.

[TomC]

I have almost 10mV improvement after some modifications to AOZ1094 circuit.

Here is the measurements that I had before.

The Average noise (16) at Acq. Mode is 22mV with 100us and 14-16mV with 500us (before 30-34mV)
The Sample (normal) noise at Acq. Mode is 32-40mV with the most to be btw 34-38mV (before 40-52mV).
The Peak noise at Acq. Mode is 32-44mV with the most to be btw 34-40mV (before 40-52mV).
 
The last attachment photo is what I do to adapter board.

That's excellent!
With that low average noise you shouldn't have any problems triggering on low level signals!

Recently I was checking the GND noise on my scope with the ferrites on the probes which I now have permanently installed, on sample mode, the noise is no longer strong enough to allow me to trigger the scope (normal trigger) anymore.

I will soon start testing my old PSU, I've been preparing the test bed, and that includes better means of testing at mains voltages from 100-250VAC. So I'm in the process of redesigning my variable AC supply to include that facility.

[BBAAHHOO]

Hello everyone! Someone tell me - is there a new firmware? (2.8.3 above).... the official site problem ...

[lemon]

No there is no any problem at their site.
They changed the site, that operate different than previous site.

Go to the Product Service of the menu and choice Software Upgrading from the drop down menu.
Fill you serial number to the Input Sequence Number area without the last 3 digits of your sn.

Example: if you have sn with SDS71021211xxx fill with SDS71021211 and click to GO.

For mine sn the fw is SDS7102UP3.3 (they haven't release new fw from April).

[BBAAHHOO]

Got it. Thank you.

[lemon]

I have almost 10mV improvement after some modifications to AOZ1094 circuit.

Here is the measurements that I had before.

The Average noise (16) at Acq. Mode is 22mV with 100us and 14-16mV with 500us (before 30-34mV)
The Sample (normal) noise at Acq. Mode is 32-40mV with the most to be btw 34-38mV (before 40-52mV).
The Peak noise at Acq. Mode is 32-44mV with the most to be btw 34-40mV (before 40-52mV).
 
The last attachment photo is what I do to adapter board.

That's excellent!
With that low average noise you shouldn't have any problems triggering on low level signals!

Recently I was checking the GND noise on my scope with the ferrites on the probes which I now have permanently installed, on sample mode, the noise is no longer strong enough to allow me to trigger the scope (normal trigger) anymore.

I will soon start testing my old PSU, I've been preparing the test bed, and that includes better means of testing at mains voltages from 100-250VAC. So I'm in the process of redesigning my variable AC supply to include that facility.

The one day I was happy the other day was unhappy!
Now, I have problem with the measurement by long gnd lead.
Look at the attachment captures.
With the short gnd clip everything is OK but with the long gnd lead everything is bad.

Now I must looking what went wrong...
The signal is clearly from noise but has oscillation.

[TomC]

I have almost 10mV improvement after some modifications to AOZ1094 circuit.

Here is the measurements that I had before.

The Average noise (16) at Acq. Mode is 22mV with 100us and 14-16mV with 500us (before 30-34mV)
The Sample (normal) noise at Acq. Mode is 32-40mV with the most to be btw 34-38mV (before 40-52mV).
The Peak noise at Acq. Mode is 32-44mV with the most to be btw 34-40mV (before 40-52mV).
 
The last attachment photo is what I do to adapter board.

That's excellent!
With that low average noise you shouldn't have any problems triggering on low level signals!

Recently I was checking the GND noise on my scope with the ferrites on the probes which I now have permanently installed, on sample mode, the noise is no longer strong enough to allow me to trigger the scope (normal trigger) anymore.

I will soon start testing my old PSU, I've been preparing the test bed, and that includes better means of testing at mains voltages from 100-250VAC. So I'm in the process of redesigning my variable AC supply to include that facility.

The one day I was happy the other day was unhappy!
Now, I have problem with the measurement by long gnd lead.
Look at the attachment captures.
With the short gnd clip everything is OK but with the long gnd lead everything is bad.

Now I must looking what went wrong...
The signal is clearly from noise but has oscillation.

Later today I'll do the same test and see what my results are for the same frequency and signal amplitude. I'll try with the probe ferrites on and off for better comparison. What I think I see on your captures is that predominant 100MHz GND noise riding on the 50mV 10MHz signal. Is that what the FFT is telling you?

[lemon]

TomC, at page 107 you have done the same test and you were OK.
At the same time I have done the same tests until 10MHz (I have 10MHz signal generator) and I was OK, too.

I changed the L2, I removed the second L and bridged this, I removed the smd capacitor next to D127, I removed the zero resistor btw the two ground planes and bridge this...but nothing! The same issue is continues...

[TomC]

TomC, at page 107 you have done the same test and you were OK.
At the same time I have done the same tests until 10MHz (I have 10MHz signal generator) and I was OK, too.

I changed the L2, I removed the second L and bridged this, I removed the smd capacitor next to D127, I removed the zero resistor btw the two ground planes and bridge this...but nothing! The same issue is continues...

Thanks for reminding me!
So many posts on noise, I didn't remember I had already tried this particular test.

Was anything different when you had good results, like the place you did the test, or where the generator was plugged in? It is always possible that the common mode noise is coming from a source other than the scope, even in that case the short ground lead will prevent it from being displayed because it will prevent it from changing to differential mode noise.

Let me know if there is anything I can do to help!

[TomC]

TomC, at page 107 you have done the same test and you were OK.
At the same time I have done the same tests until 10MHz (I have 10MHz signal generator) and I was OK, too.

I changed the L2, I removed the second L and bridged this, I removed the smd capacitor next to D127, I removed the zero resistor btw the two ground planes and bridge this...but nothing! The same issue is continues...

Lemon,
I looked some more at the images from your test and I have a suspicion that you may want to check. Looking at the signal riding on top of your 50mV 10MHz signal, I'm pretty sure this is a single frequency of about 100MHz. I suspect that this is visible, partly due to a strong 10th harmonic from the 10MHz base frequency that is being produced by your generator, and partly due to the effect of the resonant circuit formed by the long ground lead and the input capacitance of the probe. On previous experiments I've conducted (see post #1117 via the link below), I've found that this resonant frequency is in the vicinity of 100MHz.

https://www.eevblog.com/forum/testgear/review-of-owon-sds7102/msg233851/#msg233851

If this is the case, the problem should considerably diminish as you change the generator's frequency. For example, with the generator set to 8MHz the harmonics closest to 100MHz would be 96MHz and 104MHz.

[TomC]

Lemon,
Here are some captures at the frequency that looks worst on my scope, on the first two there are no ferrites on the probes and the probes are hanging down. The third capture is with the same settings but I have re-installed the ferrites on the probes. I don't think these signals are that different from what you got. I still suspect that part of the problem is the resonance of the ground lead and the probe's input capacitance. I don't remember for sure, but is possible that when I did the tests on page 107 I had already permanently installed ferrites on my probes. I tried to get those results again without the ferrites by positioning the probes differently and couldn't in the frequencies around 10MHz. When I get to around 20MHz the 100MHz ringing mostly disappears. It is worst at the frequency of the attached images.

[lemon]

TomC, your suspect that part of the problem is the resonance of the ground lead and the probe's input capacitance, probably is true but I have the suspection that to me there is adding problem.\

I add some ferrites to the probe, nothing the same.
I change the generator frequency from 4-10.9MHz nothing the same.
From what I see there is a ringing to all frequencies.

Look at the attachments. At the first I connected the probe to signal generator output with ac mains off....what is this?
If I turn the switch on of the signal generator I have always the same ringing (see at the 4.1MHz), if I lower the amplitude of signal generator until very low the signal will be the same like complete closed!

[TomC]

TomC, your suspect that part of the problem is the resonance of the ground lead and the probe's input capacitance, probably is true but I have the suspection that to me there is adding problem.\

I add some ferrites to the probe, nothing the same.
I change the generator frequency from 4-10.9MHz nothing the same.
From what I see there is a ringing to all frequencies.

Look at the attachments. At the first I connected the probe to signal generator output with ac mains off....what is this?
If I turn the switch on of the signal generator I have always the same ringing (see at the 4.1MHz), if I lower the amplitude of signal generator until very low the signal will be the same like complete closed!

I think that first capture the generator is acting as an antenna because is off. It looks like a lot of radiated power coming from somewhere, and the large ringing is close to 10MHz, the small still 100MHz.

I also get ringing in frequencies like 4MHz without ferrites on the probes, however, I still can trigger on the low level signals, anything around 40mV or higher I can trigger OK even if there is ringing. With the ferrites on the probes most of this ringing disappears. I use two ferrites on each probe, the type that you normally use for power cables, one near the BNC, and the other near the probe. The probe cable is looped once around each of these ferrites for double the inductance. Is that the way you setup your ferrites? I would have expected that to help your ringing, because it looks so similar to mine.

[lemon]

I use two ferrites on each probe, the type that you normally use for power cables, one near the BNC, and the other near the probe. The probe cable is looped once around each of these ferrites for double the inductance

TomC, No I used two ferrites without any looped to cable. I'll do a test like this and reply about this.

Attention the following information is from Adapter Ver. 3.0
I upload some measurements captures from the AOZ circuits as I modificated this at the last.
Unfortunately the initial referenced measurements had limited BW (20MHz) and I can't to compare with these that is full BW.

But,  there is one measurement with a full BW that with D127 180°turn modification (this method decrease almost 40% the noise). This measurement has taken at the output of 5.5V after the C45 capacitor. Upper is waveform from 5.5V output, bottom is gnd-noise.


The 5.52V Output.png is the measurement at the same position as before but now is at the last decoupling capacitor after the second 5R6 inductor. There is another timing than before, 200ns vs 100us but the level of noise is significantly lower than previous measurement (28mVp-p with 10X attenuation = 2.8mVp-p with 1X). The previous measurement was 74mVp-p (10X).
I am very sure that if I capture with the 100us the noise will be bigger but sure very lower than 74mVp-p.
The second yellow waveform is the gnd-noise capture.

The AOZ1094.png is the capture with the probe tip over the chip. As you see there are some signs that related to some spikes at the yellow waveform (gnd-noise). Sure there is need to investigate that but I don't know if that is normal or my AOZ is defected from many soldering-desoldering that I make to all this area of circuits.

The D127.png and L3.png is the captures with the probe over of them. They have identical pattern. At this point, I had some measurements with decoupling capacitor or no at the cathode of diode. The decoupling capacitor is minimize at little the ringing of pulse and for that reason I applied it.

At the end there is no any measurement on the last 5R6 Coiltronics inductor. It is shielded and you can't to record any waveform over this.

I think that the modification of this area has reached its limits given the existing circuit topology. There is one option, yet. The replacement of second inductor by ferrite with a very low DC resistance.

Now I'll focus to the crappy LED Circuit Backlight.

[lemon]

Lemon,
Here are some captures at the frequency that looks worst on my scope, on the first two there are no ferrites on the probes and the probes are hanging down. The third capture is with the same settings but I have re-installed the ferrites on the probes. I don't think these signals are that different from what you got. I still suspect that part of the problem is the resonance of the ground lead and the probe's input capacitance. I don't remember for sure, but is possible that when I did the tests on page 107 I had already permanently installed ferrites on my probes. I tried to get those results again without the ferrites by positioning the probes differently and couldn't in the frequencies around 10MHz. When I get to around 20MHz the 100MHz ringing mostly disappears. It is worst at the frequency of the attached images.

I done one measurement of 10MHz at 40mV output. Two large ferrites with each of them with one looped cable inside.
Yes there is an improvement but without right triggering. The reason of this is that I have removed all the mods to the Led Back-light Circuit and for this time the gnd-noise has increased.

[TomC]

I done one measurement of 10MHz at 40mV output. Two large ferrites with each of them with one looped cable inside.
Yes there is an improvement but without right triggering. The reason of this is that I have removed all the mods to the Led Back-light Circuit and for this time the gnd-noise has increased.

Nice!
I think it will get even better when you put the mods back in.

[lemon]

Some Observations on LCD Backlight Circuit about (Adapter Version 3.0).

The adapter version 3.0 has an unique design. The output of 5.5V divided at two parts. The first one (right side) supplies the main board, the second one (left side) supplies the LCD Backlight Circuit (and go on...).

The unique design divides not at the end of the right side after the decoupling capacitors but direct to the L3 output.

Look at the photo "Adapter mods2".
If you measure at Point A that is the 5.5V output to mainboard the result will be the photo "5_6 Output to Mainboard".
If you measure at Point B that is the output of L3 the result will be the photo "L3".
If you measure before L2 (input) the result will be the photo "Input before L2", at the end the same measure after the L2 inductor is the photo "Input after L2".

What crappy design is this?

The input ripple to L2 is very big and of course this effect to the gnd-noise.
If you see the output waveform, will be the photo "Output C35". This measure is done at the ends of C35. My multimeter displays at this point 8.765 Vrms (I had 0% the backlight position)

At the next stage I am going to investigate more this area of circuit and I'll try to eliminate this behaviour.

Here is some measurements captures with the probe over the components without gnd connected.
D1X = over the diode
IC = over the IC S126k
L2 = over the inductor L2