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Review: Hantek DDS 3X25. Anyone own one?

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torch:
In playing with Mecha's and Marmad's software, I have discovered that my DDS3x25 does not faithfully generate certain waveforms (square, triangle and sawtooth) at low frequencies. Here's a "square" wave:



The maximum voltage is ~2 times what it should be and the shape will be nothing like it should be. Increasing the frequency, the amplitude is almost correct by 25hz

This happens with any control software (including Hantek's) and stand-alone on start-up when saved as the default waveform.

Oddly enough, it does not happen with sine waves. Sine waves have reduced amplitude at reduced voltage but maintain the correct shape.

Talking to Mechatrommer by PM, his DDS3x25 does not exhibit this curious flaw. Is this just mine or can anyone else reproduce this behavior?

amspire:
It all looks OK.

Your Rigol is probably spec'ed for a 50 ohm output. If so, an open circuit output will be double in voltage to the amplitude settings on the Rigol. That is normal for a 50 ohm output from a generator.

The waveform is OK to. You probably have the scope set to AC coupling, and that would be the correct waveform for AC coupling at 1 Hz squarewave.

Richard

torch:

--- Quote from: amspire on August 15, 2011, 03:11:03 am ---Your Rigol is probably spec'ed for a 50 ohm output. If so, an open circuit output will be double in voltage to the amplitude settings on the Rigol. That is normal for a 50 ohm output from a generator.
--- End quote ---

The Rigol has 1Mohm inputs. The Hantek was also set to 10 Mohm impedance. I was using co-ax (RG58/U) and tried it with and without a 50 ohm terminator. Yes, it affects the amplitude, but does so consistently. That is, this variation in amplitude:frequency occurs with or without the terminator.


--- Quote ---The waveform is OK to. You probably have the scope set to AC coupling, and that would be the correct waveform for AC coupling at 1 Hz squarewave.
--- End quote ---

Ding ding ding ding ding!!! WE HAVE A WINNER!

And I have egg on my face.  :-[

Yes, the Rigol was indeed set to AC coupling, and yes, setting it to DC corrects the waveform -- AND corrects the voltage fluctuation.

Thanks Richard.

TT89:
Heya,

Been watching this conversation for a few months and now I decided to open my mouth and say: great job done! Really appreciate all the efforts done to make this potential device even more potential.

Although  ;D I have a bit of a problem that I thought sharing with you.

After having done the setup installation as instructed, and with different windows support settings, and used administrative priviledges, just to close possibility of typical windows related installation issues, I am still having problem with the startup of the program. On a side note, there were no any visible problems/errors with the installation. Even the installation file that the installer made looked error free to my eyes.

So to the main issue:

When I start Goltek controller, despite of it's installation location C:\ or D:\, despite of what settings I used, it starts up with series of an errors:


--- Code: ---"Error while reading data 1. Type mismatch. Aborting and save read data. File=C:\xx\xx\xx\goltek101\sine.csv"
--- End code ---
(attachment 1)

And it basically goes through all those csv files, except square.csv

Then it says:

--- Code: ---[i]Type mismatch. Resetting phase profile. Please restart application.[/i]
[i]Type mismatch. Resetting signal profile. Please restart application.[/i]
--- End code ---

After this, only square wave form works, and it seems to work perfectly. All other forms does not work, but show the same signals.
(Attachment 2. Plain signal on output channel, yet synch channel seemed to produce correct square signal at correct frequency as far as it stays as square.)

My OS would the mother of all software problems: Windows 7 64-bit Ultimate.    ::)
Hantek driver seems to work fine, since I used DDS-3x25 USB application, a.k.a the Hantek's one they supply. All waveforms there looked decent, but only examined that swiftly.
Been excited to play with my new Hantek DSO5120B oscilloscope so I haven't had much time to examine this problem any further yet.

Again thanks for the time spend on this little magicbox!

Regards,

Almost happy EEstudent.  :P

Mechatrommer:
PM'ed you TT89. we'll see whats your problem. btw, i've finished goltek capture 100a and modify a bit goltek controller 103a. :P http://www.soasystem.com/eng/goltek/goltek103.zip

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