Author Topic: EEVblog #474 - GW Instek GDS-2000A Series Oscilloscope Unboxing & Fi...  (Read 53755 times)

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Offline Hydrawerk

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In fact, on the Rigol, you can just run the Trigger Out back into channel two and use the frequency counter to see the waveform rate. (...)
Possible on DSOX2002A, too.
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Offline vk6zgo

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Now that is DUMB..
Two BNC's in the front for what?
If they both perform the same what is the advantage, being able to swap to BNC 1 or BNC 2, now that is really dumb..

The output probably depends on which hole the module is in.

If you have two FG modules,you presumably have two separately adjustable generators which may be useful in some circumstances.
That said,the implementation is pretty poor for an instrument aspiring to this price range.

In general,the clunky UI,& lack of a real equivalent of an analog display is pretty off-putting.
If I ever was going to shell out $2000 plus for a DSO,it wouldn't be this one!
 

Offline marmad

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i don't think you can speed up data capture by reducing grading depth, DPO-core will simply add data and run next capture, display processor will count
depth value and calculate color/grading. This can only have influence on UI speed, especialy when doing measurements on the accumulated wave "depth" data.

Btw, 16 levels was 12 yrs ago a good value for state of the art DSOs:

http://www.hit.bme.hu/~papay/edu/DSOdisp/gradient.htm
Very interesting link, tinhead - thanks for that! I hadn't seen a clear explanation of different methods for implementing intensity (combined with decimation) before. But given that there are so many methods outlined, I still think it's possible that levels of gradation might affect waveform update speeds - depending on how the calculations are performed. For example, with Tek's DPO architecture, they have the Acquisition Raterizer ASIC which processes captured waveforms to a 21-bit deep buffer. I would imagine that the rasterization process might be faster (thus allowing more input - i.e. captured waveforms) if the buffer were only 4-bit deep.

One thing that would interesting to know for all of the current DPO-like competitors in this price range (Agilent, Rigol, Instek), is how they implement persistence - when combined with intensity grading. I analyzed captured waveforms on the Rigol and found the following results:

The small scale at the bottom of the screen contains 64 levels of grey.



The following are the brightness levels (HSB) of a single waveform (STOPped) depending on the persistence and intensity settings - shown as minimum to (50%) to maximum intensity scale:

a) Min persistence (closest setting to NO persistence on the Rigol):  44% - (64%) - 84%
b) Any persistence setting between 50ms - 20s:  4% - (14%) - 24%
c) Infinite persistence:  7% - (27%) - 47%
« Last Edit: May 28, 2013, 10:22:11 am by marmad »
 

Offline EEVblog

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FYI there is a review of the GDS-2000A scope in this months Silicon Chip mag.
I noticed a few errors, and no mention of the function gen module limitation, or lack of fine control. Wasn't really an in-depth review.
 

Offline thefatmoop

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not sure why this comment was marked as spam on youtube...

I read a pdf teardown on the 100mhz 1000 series instek scope and the ADCs were overclocked.Wouldn't be surprised if you find that in this model. The volts/div big knobs are just plain awful and have a tendency? to register in the wrong direction when turned slowly. The instek 1000 series menus and theme is darn close to a copy of the archaic tektronix DSOs!

teardown here btw
http://welecw2000a.sourceforge.net/docs/Hardware/GW_Instek_GDS-1152A.pdf


Stay away from instek. if you need a cheap scope get a rigol.
« Last Edit: May 28, 2013, 11:36:54 am by thefatmoop »
 

Offline Teneyes

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I analyzed captured waveforms on the Rigol and found the following results:
The following are the brightness levels (HSB) of a single waveform (STOPped) depending on the persistence and intensity settings - shown as minimum to (50%) to maximum intensity scale:

a) Min persistence (closest setting to NO persistence on the Rigol):  44% - (64%) - 84%
b) Any persistence setting between 50ms - 20s:  4% - (14%) - 24%
c) Infinite persistence:  7% - (27%) - 47%
   aaaH , Thanks Marmad
   Now a bit  off topic.  It is hard for me to think that some persistence ( 50ms) is less light than No presistence, I guess I will have to accept (scaling, to show variations)
Also what is the meaning of Persistence in a single shot. After ghosts??  ;D
IiIiIiIiIi  --  curiosity killed the cat but, satisfaction brought it back
 

Offline marmad

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   Now a bit  off topic.  It is hard for me to think that some persistence ( 50ms) is less light than No presistence, I guess I will have to accept (scaling, to show variations)
Also what is the meaning of Persistence in a single shot. After ghosts??  ;D

Well, it would be nice to know the exact formula being used. But it seems with the 'Min' setting on the Rigol, it means the intensity gradation is based purely on the waveforms per second. But when you start adding a persistence value to the mix (which is a frequency between 0.05 - 20Hz - or infinite), the base level needs to be different - perhaps in order to be additive.

Attached is an image of noise @ Min / 50ms / Infinite persistence (all with 100% intensity).
 

alm

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Some people include links in the description to the correct spots in the video, kind of like a table of contents.
 

Offline Pinkus

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I know you might not like this, but sticking to some kind of script might also make future reviews more concise ...
While this is true of course, it would make the videos from Dave more boring. I am watching them with great fun because one cannot predict what will happen, what Dave likes and what he will rant about.... and of course I am watching his videos because I may learn something. Thats edutainment.
And by the way: this was not a review: it was unboxing and playing around.
Peter
 

Offline Stonent

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I did think the menu system on this scope looked very 16 color-ish.
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Offline marmad

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I did think the menu system on this scope looked very 16 color-ish.

Because, unfortunately, it is only 16 colors. One thing Dave didn't like - and described as looking like the DS1052E (or something to that effect) - is the fact that GW-Instek is only using an 8-bit (256) color display (like last-generation inexpensive DSOs) instead of the more modern 16-bit (65,000) ones. 

i don't think you can speed up data capture by reducing grading depth, DPO-core will simply add data and run next capture, display processor will count
depth value and calculate color/grading.

Except, of course, we now know there is no dedicated display processor - only the acquisition/display FPGA (tied to both sample and display memory) and the Blackfin. So I would say, yes, using 4-bit grading and only 256 colors for the LCD would make it possible to speed up data capture, given their design.
« Last Edit: May 30, 2013, 12:03:21 pm by marmad »
 

Offline tinhead

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... the fact that GW-Instek is only using an 8-bit (256) color display (like last-generation inexpensive DSOs) instead of the more modern 16-bit (65,000) ones. 

that display connector didn't looks like 8bit.



Honestly i don't know if there are any manufacturers using less than 16bit displays in their DSOs, Siglent even claims to have 32bit.
Of course what the firmware (actally the developer) is then dong with these available colors is different story, from the hardware point of
view there should be no DSOs with 8bit display since 3+yrs.

Btw, less funny are the option slots ... look at the picture:



so no room for LAN/GPIB when VGA or SG or LA inside ... hmm
EDIT: so no room for LAN/VGA when GPIB or SG or LA inside ... hmm
« Last Edit: May 30, 2013, 02:57:47 pm by tinhead »
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Offline marmad

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that display connector didn't looks like 8bit.

Honestly i don't know if there are any manufacturers using less than 16bit displays in their DSOs, Siglent even claims to have 32bit.

Man, you are really clinging to your defense of this scope. ;)   Anyway, IMO, however you want to quantify it - their color handling (and grading) is sub-par compared to similar price range DSOs; at least in terms of 2 channel models - for 4 channels the trade-offs might be worth it.

Does it work? Yes. Does it look good? IMO, no. Even for color grading, using 64-bits reveals much more detail - and a better looking waveform display.
« Last Edit: May 30, 2013, 02:01:28 pm by marmad »
 

Offline marmad

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so no room for LAN/GPIB when VGA or SG or LA inside ... hmm

That's a combined LAN/VGA module - and the GPIB module is separate - although, yes, you're right, you can't have LAN/VGA, LA, and FG all at the same time.
 

Offline grego

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Honestly, you don't want the FG as it is right now.  That's not to say they won't release a new FG module later but the current one - meh - for the same price get a dedicated device with a heck of a lot more functionality.

The slots are pretty easy from my perspective - LA and VGA/LAN.  That's just me though!
 

Offline marmad

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The slots are pretty easy from my perspective - LA and VGA/LAN.  That's just me though!

Agreed.
 

Offline tinhead

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Man, you are really clinging to your defense of this scope. ;)   


oh my gosh, no! It was only hardware fact, nothing else. That what we see on screen, by given hardware, is
actually confirmation for bad/not that good/not the best implementation, which seems to be general low-costs DSOs issue.


The slots are pretty easy from my perspective - LA and VGA/LAN.  That's just me though!

Agreed.

the slots (idea) itself is ok in my opinion, it is more the fast that you can have only 2 at same time,
so no chance to have LA/SG inside and remote control over LAN/GPIB or watch on VGA simultaneously.
I don't want to be human! I want to see gamma rays, I want to hear X-rays, and I want to smell dark matter ...
I want to reach out with something other than these prehensile paws and feel the solar wind of a supernova flowing over me.
 

Offline vk6zgo

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that display connector didn't looks like 8bit.

Honestly i don't know if there are any manufacturers using less than 16bit displays in their DSOs, Siglent even claims to have 32bit.

Man, you are really clinging to your defense of this scope. ;)   Anyway, IMO, however you want to quantify it - their color handling (and grading) is sub-par compared to similar price range DSOs; at least in terms of 2 channel models - for 4 channels the trade-offs might be worth it.

Does it work? Yes. Does it look good? IMO, no. Even for color grading, using 64-bits reveals much more detail - and a better looking waveform display.

No doubt the colour grading display is useful in some circumstances,but in my opinion,a line rate video signal is not a good test of this facility,as for this waveform,colour doesn't provide any significant improvement compared to that from a conventional DSO display

An analog display or a normal DPO display is more useful for such a waveform.
 

Offline marmad

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No doubt the colour grading display is useful in some circumstances,but in my opinion,a line rate video signal is not a good test of this facility,as for this waveform,colour doesn't provide any significant improvement compared to that from a conventional DSO display

I guess you haven't been following the discussion. This wasn't, in any way, a demonstration of when or where color grading is useful. The image was merely intended as an illustration of the extra detail visible with more levels of grading - and it was just an image I had handy to convert to 64 / 16 levels of color grading. Whether you, personally, think the extra detail visible with 2 more bits of grading is 'significant' - is another matter.
 

Offline mike1305

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FYI there is a review of the GDS-2000A scope in this months Silicon Chip mag.
I noticed a few errors, and no mention of the function gen module limitation, or lack of fine control. Wasn't really an in-depth review.

It still absolutely cracks me up how their function generator modules operate... what are they doing?
 

Offline EEVblog

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It still absolutely cracks me up how their function generator modules operate... what are they doing?

I guess it seemed like a good idea at the time!  :palm:
 

Offline vk6zgo

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No doubt the colour grading display is useful in some circumstances,but in my opinion,a line rate video signal is not a good test of this facility,as for this waveform,colour doesn't provide any significant improvement compared to that from a conventional DSO display

I guess you haven't been following the discussion. This wasn't, in any way, a demonstration of when or where color grading is useful. The image was merely intended as an illustration of the extra detail visible with more levels of grading - and it was just an image I had handy to convert to 64 / 16 levels of color grading. Whether you, personally, think the extra detail visible with 2 more bits of grading is 'significant' - is another matter.

And,I guess you didn't really read my comment.

My point was that a line rate video signal was an unfortunate choice of image to use as an example.

To someone who has spent a long time (too long! ;D) looking at these waveforms in real life,neither display is useful,with the colour grading simply adding another level of obscurity to the presented display.

What you are normally interested in,are:
Burst shape & amplitude.
Blanking duration
Sync pulse duration,amplitude & rise time.
Chroma amplitude---excessive chroma information below the blanking level may be affected by sync pulse
amplitude adjustments,causing colour errors.

All of this information is presented,if poorly,in both the 16 bit & 64 bit examples.
The only obvious difference is in the actual video information,where the 64 bit example looks closer (not close,but closer) to an analog display.

I reiterate,my comment was upon the choice of example.
 

Offline marmad

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And,I guess you didn't really read my comment.

Yes, I did.

Quote
I reiterate,my comment was upon the choice of example.

Please feel free to spend your time creating and posting a better example - perhaps a more fruitful use of time.
 

Offline vk6zgo

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And,I guess you didn't really read my comment.

Yes, I did.

Quote
I reiterate,my comment was upon the choice of example.

Please feel free to spend your time creating and posting a better example - perhaps a more fruitful use of time.

Gee,I'm sorry if your self esteem is so tied up in this.
I thought that I was helping the discussion along.
 

Offline EEVblog

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Instek have replied on a few points, here is their response:

Quote
At 25:46, you mentioned the waveform is jerky when the statistics function is ON…
Since you did not input signals, the GDS-2000A in under Auto Trigger mode. On the lower right hand corner Trigger counter showed more than several dozens of counts, which meant that GDS-2000A was triggered by DC noise signals.(Dave used 300MHz version which has a very sensetive trigger.) Hence, the updat rate and response was a little slow. Turn up Trigger Level or set Hi Frequency Rejection will solve the problem.
 
At 43:00, you compare the AM measurement with Rigol. GDS is far behind Rigol regard to the Intensity performance.
You set the acquisition memory into “short” mode, so the envelope of the AM signal is not solid, if you change to “Auto” mode, there will be no problem.
 


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