General > General Technical Chat

Review: Hantek DDS 3X25. Anyone own one?

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torch:
Ok, I the little guys were still asleep so I downloaded the DDS3X25Ctl_0_9_1 version from page 16, hooked the output to the count in and to my Rigol and started to play. Unfortunately, they didn't stay asleep long, so I had limited time to play, but this is what I noted:

The count often differs from the generated frequency slightly. EG: 1.00000kHz produced 1.00016khz with the occasional flicker to 1.00017kHz. The Rigol displays 1.000kHz, but flickers betweeen .992 to 1.004. 3MHz produces 3.03030MHz. (Rigol displays 3.030MHz) But 4MHz produces 4.00000MHz and the Rigol agrees.

The Rigol does not agree with the voltage setting. EG: 3.5v p-p is measured as 3.6v p-p.

There is an error in setting the RMS amplitude function: Parameter input of 1.72 produced a "Human Error" message informing me that "RMS amplitude must be between 0.035355V and 3.5355V"

I think a digit gets lost when setting the sweep step. Set to 100.0Hz, it seems to climb by 1000.0Hz instead, according to the Sweep Data log.

There is a slight distortion during the transition between certain frequencies, but nothing like the earlier screenshots posted, and not detectable between some frequencies.

"Reset All" cause an error message then program crash. Couldn't catch the error message -- something not found, I think.

I tried entering "48828.125" for frequency 1, but it displayed 97.6562 kHz and output 48.8400kHz.

Ok, now I have a 2 year old d`rivi`ng his truck on my k24eyboar988d.



marmad:

--- Quote ---we cannot be sure since we (or me only?) used cheapo dso to measure, there's blind time during trigger.
--- End quote ---

Yes, I can see with my 10Mpt scope that the entire sweep is glitch-free.


--- Quote --- about the square, i believe its marmad's implementation of square wave, since i havent seen like that in my square wave. even at highest frequency of his sweep, zooming in reveals slight rise time abberation.
--- End quote ---

This has been answered once already, but here is the square wave sweep with 2 fixed bits - see attached .png.


--- Quote ---edit: i just noticed, DDSClockv2.exe can accurately estimate point length (esp at 990100Hz), but in DDSClockSource.zip is not. so they are not the same code/compilation.
--- End quote ---

Yes, when you asked me to release the code for the DDSClock, I tried to quickly clean it up a little bit for you (it was a mess) - and I see now that a small piece was accidentally deleted - I didn't have time for re-testing the cleaned code.  But if you understood the logic - or had compared it to my code posted yesterday - you would have seen the error immediately:
yesterday: lpLength = Fix(lpPeriod * lpLength)
source:    dLength = Fix(dLength)
I will make sure I release ONLY bug-free, test-resistant source in the future.  :)

You didn't respond to any of my thoughts or answer any of my questions from my previous post, and your code still gives me (for my device) the wrong answer for such things as, for example, actual output frequency at 1kHz.  I haven't heard from any other user that says my DDSClockv2 delivers incorrect answers about anything.  But if you want to duplicate/improve/develop previous work with newer versions of code, fine, but PLEASE stop publishing these comparison charts - it feels like some contest - and a bit strange.  Thanks.


--- Quote ---Ok, I the little guys were still asleep so I downloaded the DDS3X25Ctl_0_9_1 version from page 16, hooked the output to the count in and to my Rigol and started to play. Unfortunately, they didn't stay asleep long, so I had limited time to play, but this is what I noted:
The count often differs from the generated frequency slightly. EG: 1.00000kHz produced 1.00016khz with the occasional flicker to 1.00017kHz. The Rigol displays 1.000kHz, but flickers betweeen .992 to 1.004. 3MHz produces 3.03030MHz. (Rigol displays 3.030MHz) But 4MHz produces 4.00000MHz and the Rigol agrees.
--- End quote ---

Thanks very much, Torch. I will go through your bug-list later. Please note however, that the DDS3X25 doesn't always provide perfect frequencies - if you ask for 1.000kHz, you actually get 1.00016kHz due to the clocking formula and the logic of the device.  I have been trying to explain this to Mecha to no avail. The frequency counter on the Hantek is more accurate than the one in the Rigol - because it's easier to count frequencies if that's all you're doing with a hardware input.  The Hantek corresponds perfectly with my Fluke counter - trust the count on the 3X25 - not the Rigol.

Edit:  Whoops - forgot the CSV files...  :-[

Edit:  Got rid of the stupid stuff...  :P

marmad:

--- Quote ---I am not here to fight for credits, instead, if I can, I would just like to promote more openness.
--- End quote ---

Absolutely, I thought that's what it was about as well.


--- Quote ---A related quastion is: did you or can you publish your SweepTest code?
--- End quote ---

The Sweep Test is a big mishmash of un-commented, altered code from the DDSControl software I published even earlier - I think it is 175k with 2k being actually used  :P So it's worthless to try to sift through all of it.  But I can publish the relevant sections if you'd like - but I need some time to extract it and make it bullet-proof - once bitten twice shy  ;)  But given the info in the thread, it's really easy to make your own.


--- Quote ---You said you can sweep 1-40kHz glichless and using 2500 pts. May I ask how many periods (of a given "frequcecy") have you placed in this 2500 pts waveform? One?
--- End quote ---

Yes.


--- Quote ---2). In my last post, one can as well do DDSDownload(waveform,4) with just 0,v,0-v in the data. On this point, I feel we are still not understanding each other.

--- End quote ---


--- Quote ---Did you try placing 2 or more periods  (upto >1000) from the same "frequency" and waveform into your 2500 pts data set. If you put 2 periods there,  the sweeping range will be 2-80kHz. Right?  Then, you see glitchs?
--- End quote ---

Ok, yes, sorry, I wasn't getting your meaning until now.... yes, it's totally possible to increase the number of periods and get glitch-free sweeping above >50kHz in this fashion - it's just that the Sync Output would not correspond.

I will do a sweep like that for you now.  :)

Edit:  @onlooker - So here is a .png of a small portion of glitch-free log sweep from 1kHz to 800kHz using extra periods to increase the DAC frequency - it works fine, but notice the Sync out is locked to total periods, not frequency.   But in this regard, your original proposal was technically correct - and I was wrong - I stand corrected  :)

Edit2:  @onlooker - Here it is finally - now that I finally understand what was asked of me  :P - a portion of your requested sweep with 4000 points and 1000 periods - it sweeps from 100kHz to 50MHz glitch-free, but with the Sync locked to periods.  The .png shows the changeover from 100kHz to 200kHz.

torch:
Just stole a few minutes while SWMBO had the boys outside. It won't accept 1,000,000 but rounds up to 100.000MHz if you enter 999,999. The really cool thing is that it actually displays a fairly decent sine wave at that frequency -- something that didn't happen with the Mechatrommer software! The display on the Rigol is a bit jittery when set to real time aquisition but pretty stable when averaged 16x. The counter shows "0.00000 Hz" at that frequency, but the Rigol measures it to be 100.0MHz with the odd flicker to 99.9MHz.

marmad:

--- Quote --- It won't accept 1,000,000 but rounds up to 100.000MHz if you enter 999,999.
--- End quote ---

He,he... yeah - sorry - that's just lazy coding to avoid dealing with > 8 digit numbers  ;)


--- Quote ---The really cool thing is that it actually displays a fairly decent sine wave at that frequency -- something that didn't happen with the Mechatrommer software!
--- End quote ---


Hmm... I'm pretty sure Mecha's software did the exact same sine at that frequency.


--- Quote ---The counter shows "0.00000 Hz" at that frequency, but the Rigol measures it to be 100.0MHz with the odd flicker to 99.9MHz.
--- End quote ---

Yes the Hantek counter starts to craps out above 50MHz - I think the logic is sampling the input pin at master clock (200MHz) / 2.  Which would give it the Nyquist limit of 50MHz accuracy.

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