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| Review: Hantek DDS 3X25. Anyone own one? |
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| Mechatrommer:
--- Quote from: BoredAtWork on February 11, 2011, 08:06:42 pm ---...or they just want to impress. --- End quote --- you confirmed what i had in mind ;D but since this unit is already a small form factor compared to bench generator, make it smaller will become more advantagous imo, to save more space, rather than merely to impress people. they should know who they dealing with (not the smart combed hair and nice tie guy). |
| saturation:
I wonder if the basic design simply lacks the added tracings used in the other model DDS based generators? Only buyers of the 3005 can tell if they took photos so we can compare PCBs. It would be a design efficiency to sell 2 tiers of products, they simply don't need to redesign the PCB wholly, just append the missing traces from their routing software that currently is just a huge ground plane. --- Quote from: Mechatrommer on February 11, 2011, 03:26:53 am ---nice simplistic porn photos. i'm looking forward to take apart my unit. i just wonder why there is so much pcb area (bottom part) but i'm concern about the delay that will be introduced by pc->generator->output and input->oscilloscope->pc with the DUT in between. will it not give some effect to the graph plot or analysis? i need to study more on this. --- End quote --- One can expect delay or shifts by adding cables, adapters, etc., dependent on frequency, and the Lissajou can show you the shift. The question is is it significant for the DUT? Only the DUTs performance can say, it depends on its engineered tolerance to variation. Regardless, the 3x25 comes with a phase shift adjustment so you can try to compensate for a shift, to get the signals in sync between 2 devices. |
| bekir:
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 |
| tinhead:
--- Quote from: saturation on February 11, 2011, 12:47:14 am ---Hantek's web site has been down for a while, but its up and all its operational software are online to be downloaded for trial as you please. http://www.hantek.com.cn/english/produce.asp?classid=30 However, there is something wrong with the 3x25 rar file, its 22MB long but when unrared only drivers are viewable. --- End quote --- just rename it to iso and burn or mount. |
| Mechatrommer:
thanx bekir for your info (esp on opamp failure warning). i'm looking forward to to see how the 3x25 works as vna. my 3x25 arrived today, made a quick run and take apart for the "first" evening/night test. i'm not intending to do full performance test as saturation did, just a rough one. here are some photos. a) my unit labeling differ from the pic in documentation (no 50ohm +-3.5V max label, 350mA max etc), so not sure why. construction material not so impressive, ie uneven plastic casing color, its like its been ages. and it dont come with cd and manual, as advertised by the seller. have to download manually the software from the net, but i dont mind, as seller included free gift with it (happy customer here) b) how to take apart. c-h) the porn. i) this is how i read the signal, pls correct if i'm wrong. i just directly connect the bnc cable generator to rigol, no 50ohm termination or fancy stuff. i'm not really good at it. j) while analyzing the vb code sample, this unit just generate sin wave using precalculated 2083 points sample using sine formula. --- Code: --- Function myCreateBuf() Dim i As Integer Dim tmp As Double Dim arBuffer(4095) As Integer 'waveform buffer For i = 0 To g_nWavePointNum 'sample value tmp = g_offset / MAX_VOLT + g_amplitude / MAX_VOLT * Sin((i / g_nWavePointNum) * 2 * PI * g_nWavePeriodNum) tmp = 2048 - 2047 * tmp If tmp > 4095 Then tmp = 4095 ElseIf tmp < 0 Then tmp = 0 End If arBuffer(i) = tmp Next result = DDSDownload(g_iDevice, arBuffer(0), g_nWavePointNum) End Function --- End code --- so i just changed the sin to tan... --- Code: ---tmp = g_offset / MAX_VOLT + g_amplitude / MAX_VOLT * Tan((i / g_nWavePointNum) * 2 * PI * g_nWavePeriodNum) 'SOA MODIFIED --- End code --- then i got a cropped tan signal... just for fun. and... i've broke the warranty seal on the side of the unit :P |
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