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Hantek2d42 bugs report

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Post time 2019-2-14 13:11:30 | Show all posts |Read mode
Edited by OASJ2YSeeEhBQo1 at 2019-3-16 12:15

Hello Amy, how was the Holidays, I hope you have enjoyed it.

So I have a new handheld 2D42 and I'm enjoying it so far but I found some bugs that I would like to report, if you don't mind:
FW: 2019011101
PCB: 0000001
FPGA: V02

1- In oscilloscope mode, pressing Autoset button does not limit the memory depth
Description: Activate only one channel, let's say CH1. Change memory depth from 3k to 6k. Keep only CH1 on and apply a signal to CH1 and CH2. Press Autoset button. The memory depth won't be limited automaticaly to 3k and you will see both waveforms on the screen all crazy, as the data is broken. Setting de mem. depth manually to 3k solve it. Fixed (in FW 20190220001)
If you turn on CH2 by pressing Channel -> CH2 -> On the memory depth is automatically limited to 3k, that is fine.

2- In DMM mode, selecting the Buzzer function using the arrow keys ">" or "<" does not activate the buzzer and it is silent I need do press F3 for it to work. Fixed (in FW 20190220001)

3- This one is probably a hardware limitation/problem. In th AWG mode, the waveform is clipping on the negative side as I increase the amplitude to near the 2.5V limit or if I set a negative offset (see picture)


4- The jitter of the AFG is pretty horrendous, specially with frequencies over 1MHz. Is that normal?



5-Waveforms presents some artifacts under various settings of frequencie and amplitude (I am still trying to isolate this one)


regards,





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Post time 2019-2-14 15:58:54 | Show all posts



Sir, thanks for your feedback.
Our engineer will modify.

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Post time 2019-2-16 20:36:29 | Show all posts
Edited by gf1 at 2019-2-17 18:53

... In th AWG mode, the waveform is clipping on the negative side as I increase the amplitude to near the 2.5V limit or if I set a negative offse...

I'm facing the same issue as well on my 2D72. I measure a supply voltage of +5V / -3.3V on the output amp (EL5166) of the AWG. According to the datasheet, the output of the EL5166 can swing to within 1V of either supply rail, so -2.5V is actually beyond this limit. Fixing this issue would IMO require a hardware change (i.e. increase the negative supply voltage of the amp).

The jitter of the AFG is pretty horrendous, specially with frequencies over 1MHz. Is that normal?

  • Since the AWG's DAC is clocked at 250MSPS, the pulse width of both, the positive and negative pulse of the quare wave, can only be an integral multiples of 4ns. If the selected frequency does not grant this, then some of the pulses need to be streched or shortened in order that the generated frequency is correct  on average.
  • Additional (theoretical) limitations are imposed by the way how Direct Digital Synthesis (DDS) works. One of them are phase truncation errors, but there is also the limitation that a DDS generator can only generate frequencies wich are integral multiple of DAC_clock_freqency / dds_accumulator_size, where dds_accumulator_size is a power of 2 (I don't know what's the accumulator size on the hantek series 2000).

For instance, a 5MZh square wave would fulfill the condition (1), but the DDS can't generate exactly 5MHz, due to condition (2). But the closest frequency which can be generated by the DDS generator does no longer fulfill condition (1) and also suffers from phase truncation errors. So you are rather limited regarding the square wave frequencies which can be generated "exactly" without stretching/shortening some of the pulses  (=> basically only power of 2 fractions of the DAC clock freqency).

If I try for instance 7.8125 MZh (= 250MZh / 32) on my 2D72, I get a nice square wave - but not for any arbitrary frequency.

Regarding DDS, see for instance https://www.analog.com/media/en/ ... utorials/MT-085.pdf, or one of the many other DDS resources which can be found in the internet.

EDIT:
Square waves and pulses with very steep edges and/or small pulse widths are of course the worst case waveforms forms for DDS, when they should be reproduced at higher frequencies. Sine waves are not a problem in this regard, since they are already band-limited to the sine wave frequency. But for other kind of waveforms, the resampling done by the DDS may eventually violate the Nyquist–Shannon sampling when generating signals with higher frequencies, and this implies that the signal cannot be reconstructed exactly from the sampled data.

A possible workaround you can do is to increase the rise time (and thus reduce the bandwidth) of the square wave manually, by approximating a square wave with a trapezia. If you generate, for instance, a trapezia on the Hantek 2000, with RiseDuty=FallDuty=0.08 and HighDuty=FallDuty=0.42 with 5MHZ, then you'll notice less jitter than with a 5MHz square wave - but at the cost of renouncing the steep rise time of a true square wave.



Regards,
gf1


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Post time 2019-2-17 05:31:52 | Show all posts
Edited by gf1 at 2019-2-19 03:15
Waveforms presents some artifacts under various settings of frequencie and amplitude

I'm seeing similar glitches, too, at the AWG output of my 2D72. However, I can in particular reproduce it at 2.5V output voltage (when the negative lobe gets clipped). The spikes are already present at the input of the AWG's power amp (see blue curve below), so I don't think it caused by the clipping of the amp.  I don't see any correlated gltches on the power rails, either. I'm still unsure regarding the origin of the glitches. Since I have no evidence yet for an analog root cause, I would not rule out that they are already present in the digital signal fed into the DAC. I have no logic analyzer to measure that, though.

Yellow = AWG output, blue = input of EL5166 = output of DAC902
(captured with my Hantek 6074BD)



EDIT:
I was able to reproduce it at a much lower amplitude as well, and also manged to get a stable pulse trigger on a particular glitch. Further investigations reveal, that this glitch (in the center of my screenshots below) obviously happens at the time when DAC input Bit5 goes high and Bits 6, 7, etc. go low. I guess that it is a timing issue - possibly for some (but not all) of the BitX inputs, the required setup times are not met, so that they are seen by the DAC one cycle too late. The carry-over from  bits 6,7,... to bit 5 is obviously one of the places where this happens on my device, but there exist obviously other voltage levels as well, where glitches do occur.

EDIT:
The rising/falling edges of the DAC inputs are not clean either, but show some kind of oscillation/ringing/noise. I'm not sure whether this intentional noise added by the DDS to the digital signal, or whether it is an undesired flaw of the circuit. I also can't rule out that the latter is caused by the load of the oscilloscope probe attached to the pins, however, the double-probing test (i.e. attaching a 2nd probe to the same signal) did not make much difference.


yellow = AWG output, blue = DAC input Bit5 (Bit6 in 2nd image)





-gf1


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 Author| Post time 2019-2-19 00:07:33 | Show all posts
Yeap, those are the glitches I was referring in the item 5 of may previous post. I will try to take some screen shots later and post here, with another problem I'm found on the oscilloscope.

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 Author| Post time 2019-2-19 09:45:28 | Show all posts

Just some more screenshots to ilustrate the gitches problems in the output of the AWG.



6 - Another problem I noticed in my oscilloscope is that the wave form in CH2 is deformed comparing with CH1, even if I apply the same signal to both. The problem is more visible with channels 1 and 2 turned on and at higher frequencies (around 1MHz), but the difference is noticeable with just CH2 on too. Maybe the sample rate is not enough or some problem with the interpolation calculation, I don't know



A few more images



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Post time 2019-2-22 07:37:05 | Show all posts
Edited by gf1 at 2019-2-22 18:04

What I see in 2ch_1M.jpg and 2ch_1M_sq.jpg looks mostly like random noise. The additional spikes are likely from the AWG - I guess - and not from the scope - did you use the internal AWG? And yes, CH2 seems to be more noisy than CH1. I am facing exactly the same as well, when the device is assembled. FFT does not show a peak at particular frequencies, but rather flat wideband noise. However, if I lift one PCB, so that there is a distance of about 5cm between the two PCBs (as much as the ribbon cable length allows), then this noise decreases and CH2 becomes as clean as CH1. Apparently, some noise is radiated by the processor board and picked up near the ADC inputs. I'm wondering if a shield between the boards would help? In fact the front ends behave pretty well, regarding noise. At 10mV/div, the noise level of the 2D72 is similar to the noise level of my 6074BD. [ Of course only, as long as I keep the two PBCs at distance. ]

Your other images, like deform2.jpg, look like an attempt to apply sinc interpolation to a noisy signal - this does not work well. If you want to see what was really catpured by the ADC, then select a timebase of 500ns/div or even 1us/div. You still get 125MSPS or 100MSPS with this timebase. Then freeze the capture, and zoom-in. This avoids sinc interpolation and displays the captured samples as staircase on the device (or linearly interpolated in the PC software).

gf1


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Post time 2019-2-22 13:41:22 | Show all posts
Sorry, I didn't reply in time.
About signal burrs and the waveform is clipping on the negative side, the hardware needs to be changed.
Other firmware problem, please refer to this post to update the firmware: https://www.eediscuss.com/forum. ... id=13676&extra=
We'll give you the best solution. Please wait for some days.

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 Author| Post time 2019-2-23 06:24:01 | Show all posts
Hi Amy,

Thanks for the reply. I just updated to the FW: 201902201 run I quick test and apparently the bugs 1 and 2 are fixed. I noticed the Measure window in scope mode was also changed... I will do some more in depth tests and I came back if I found anything else.
Regarding the other problems that are hardware related, would you mind to provide some more details?

To @gf1: I tested using the internal AWG and a HDG2002B function generator,  I tried various setup configuration, using coax cable with and without 50ohm termination, x10 probes, signal output from same channel and from 2 different channels of the awg. I also tried the BW limit on and off, nothing makes a difference that's why I don't think the problem is only noise, let's wait to see if Hantek can give us a better explanation.

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Post time 2019-2-23 23:28:46 | Show all posts
Edited by gf1 at 2019-2-23 23:36

At the moment I'm facing the following noise issue:



These artifacts do happen, when the device is connected to the PC and if the windows software is collecting data. If I stop data collection in the PC software (i.e. press the pause button in the toolbar), then these artifacts disappear on the display of the device (which continues capturing and displaying data). If I continue data data collection in the PC software, the artifacts are back again. I also managed to trigger and capture this noise alone, without any signal connected to CH2 (input terminated with 50 Ohm resistor), see following image.



For better resolution I have also calulated a 1200 point FFT from the saved data (unfortunately, the PC software is still limited to saving only 1200 data points, even though capture buffer is 3k).




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