General > General Technical Chat
Review: Hantek DDS 3X25. Anyone own one?
<< < (13/108) > >>
saturation:
great work!  mechatrommer, I was looking at your photos and now they are gone!  but no worries; look forward to what you have to post.  Much to study, will analyze and report back.

Great work too bakir, I have some questions for how the Hantek failed, will analyze your post shortly.

Thanks for tip, tinhead!
Mechatrommer:
i keep getting broken upload (disconnected) just now... still attempting... continue here, sized down from fullsize pictures (c-h)
Mechatrommer:
i noticed some last minute hand soldering on the pcb. my pcb ver is 1.4, so go figure. cosmetic-wise, its not so impressive, but from rough functional test, i think its good for money and can do me some usefull work. the usb chip, main mcu and another chip after it have been erased.
saturation:
Thanks bekir, when you replaced the signal generator that broke, did you repair it yourself, or bought a new 3x25?

I see from mechatrommer's photos the op amp is a LMH6702 and the comparator is TI TL3016; that's a pretty good op amp by the way.

To prevent further damage in high output tests you can put another op amp infront of this op amp and isolate it, just configure it as a voltage follower.

From your tests, did you check the quality of the sine wave output on any higher end equipment you have in your lab?  Particularly, what is the harmonic output of the sine waves; I'm just curious.  I only have a Rigol 1052e but I get nothing at its noise floor which is about -50 dBc.  A more sensitive instrument might show that the sine wave output is hifi audio quality, i.e., -90dBc or more.

Yep, we discussed using the Hantek as a source for making VNA calculations, I use Lissajou figures to make qualitative measurements for phase delay,  we just discussed this, find our threads on measuring phase shifts and the Hantek.

Your prime number test is interesting, to superimpose them, do you have multiple sine wave sources and measure simultaneously or did you send each prime individually then merge the waveform data?

Sorry, I have no Mathlab, so can't assist in your need there.



--- Quote from: bekir on February 23, 2011, 09:50:51 am ---Hi,

I have been using DDS-3X25 and DSO-2250 USB for about two years. I must say that they are very cost effective but you have to be careful. Signal generator broken once and oscilloscope broke twice. I do not know the actual reason (no high voltage input/short circuit at probes), believe me I was very careful. Anyway just a reminder do not leave them powered up (connected to pc) while not using.
* Op-amp at the exit stage of DDS broke had to replace it (bought online directly from manufacturer as sample).
* Same op-amp that is used in the input stage of oscilloscope broke (thank gos i bought one as replacement :) ).
* A diode in the input stage of oscilloscope broke (salvaged a replacement smd diode from an old lcd projector).

Besides all these I am happy with them. Now to the main topic.

I am using these to as VNA. I am not EE, so I may be wrong on selecting words. Let me explain my situation. I generate sine wave from DDS. Connect it to my network and OSC1. Connect the output of the network to OSC2. Then get the magnitudes of input (not necessary in fact) and output. Then I find phase difference between OSC1 and OSC2 and draw bode plots.

Another method i tried to superimpose sine waves that are multiple in prime numbers (i.e. if my base freq is 1hz then I impose 2,3,5,7,11,13... hz frequency sine waves (total of 18 freqs)). Run it through the network then run fft on it. To have better accuracy, I curve fit to the signal in time domain with the magnitude and phase information from fft used as initial guess value.

First one seems to work better than second one when i look at the response graphs of RC networks. In fft there is a slight difference that I don't know why it happens. I can give some example graphs if someone interested in help.

Anyway, I did all this stuff in MatLAB 32-bit (I had(!) access in our campus), I believe it can be also done in octave as long as it can call dlls. The problem rised when our university switched to 64-bit MatLAB. My m-files and functions no longer work giving dll load error. The bad part is i didn't keep the original dlls and header files that I've used in 32-bit. So, I am asking help from someone have experience with 64bit matlab dll calls. At the end I can share my functions for signal generation and oscilloscope in a toolkit or as a sample gui. Besides that if you want any graph or data to see the performance of osc or dds just let me know. But please remember I am ME so briefly explain how should i do it.

Regards,

Bekir

Ps. I am working on Win7 x64



--- End quote ---
saturation:
Thanks so much, mecha, those photos will save me the trouble of looking at mine with virgin eyes.  I think knowing the op amps may fail is a good tip, and knowing what the part is ahead of time is a good info.  The op amp used is excellent, BTW, and pricey, about $5 each.  When I do my next digikey order I'll grab a few because it has superb specs to play with.

I notice what looks like hand soldering in your photos. compared to the centerfold photos I linked earlier that looked all machine soldered:

https://www.eevblog.com/forum/index.php?topic=2170.msg33908#msg33908

The good news, is the some chips that have their parts numbers erased, are now identified!


I think the Hantek is holding its own as a poor-man's arb and 25MHz [ at least] signal source.  For $150 its still sounding like a bang for buck.  Also, when you think that Agilent wants $400 for non-educational purchase of its FG module for its new Infiniivision scopes, you know its not too bad [ the Agilent specs that Dave showed aren't that much better than this Hantek, but probably doesn't have its quirks and faults too, but nothing an electronics person can't fix.]



--- Quote from: Mechatrommer on February 23, 2011, 12:24:16 pm ---i noticed some last minute hand soldering on the pcb. my pcb ver is 1.4, so go figure. cosmetic-wise, its not so impressive, but from rough functional test, i think its good for money and can do me some usefull work. the usb chip, main mcu and another chip after it have been erased.


--- End quote ---
Navigation
Message Index
Next page
Previous page
There was an error while thanking
Thanking...

Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod