Hantek2d42 bugs report

OASJ2YSeeEhBQo1

Hi Amy,

I have a few more observations, if you allow me. Please, don't get me wrong, I really like this device and I think it has a great potential, it just need some polishing.

1- With the last FW in Scope mode, Measure window was changed from amplitude to max/min, but the values for MAX and MIN are computed with reference to the center of the screen, not to the channel cursor. So if I move the channel trace, the values changes. Fixed (in FW 2019030201)
Regarding the Measure windows I have two suggestion:
a- Add the option to choose a different parameter to measure, like Vpeak-peak, Vrms, Max/Min, amplitude, frequency, duty cycle and period. It don't need to have all types of measurement, I understand that you want to keep it simple, but having just one type is very limiting.
b- Display the values only for the channel that is active. The screen is small and there is no reason to keep showing a banner with only "????" on top of the signal I'm trying to see.

2- Connecting the USB cable to the scope adds a small DC offset to the waveform;
3- This one is very annoying: Every time the device is connected to the PC software, its settings are reset to default. The software also do not keep the last configuration used nor reads the actual settings on the device.
4- The PC software uses only 1200 data points to trace the waveform when we could have up to 6k;
5- The PC software is very slow and barely usable;
6- The AutoUpdate feature is very nice to have, but the related window need to be translated to English; Fixed (in Software version 1.1.10)

7- When using the device connected to the PC software, the configurations are not synced in both ways. If I set a parameter in the software the corresponding function in the handheld is updated but it does not work the other way around causing some problems. For exemple:

8- The PC software in DMM mode keeps logging values even while the hold or "stop collecting data" button is pressed.
9- Just a minor detail: in AWG mode setting a negative offset and then using the arrow keys "^" to increase the value will show "-0.00V" when it gets to 0V.
10- One last suggestion: add the ability for the button "Menu" to toggle the menu on and off. So when I press the button the menu is shown on the display, pressing it again will close it, this way I don't have to wait a delay time for the menu to disapear. Same for Channel, Time and Trig buttons.

gf1

@OASJ2YSeeEhBQo1:

To demonstrate how sinc interpolation can screw-up the displayed waveform (when the bandwidth of the captured signal did violate the sampling theorem) I have captured a 7.8125 MHz square wave signal from the 2D72 AWG with my 6074BD, a) with sinc interpolation and b) with linear interpolation. In order to force a reduced sampling rate of 250MSPS (in order that the result is better comparable to the 2D72), I have turned on all 4 channels.

6074BD - sinc interpolation:



6074BD - linear interpolation:



The "linear" result is likely closer to the  true waveform (square wave). And the sinc result looks almost like the waveform displayed on my 2D72 (in single channel mode) at the same sampling rate and timebase. Unfortunately, sinc interpolation is the default on the 2D72 and can't be turned off - in cases where it is undesired.

EDIT: Added the 2D72 screenshot for comparison (also 250MSPS, 50ns/div) - looks almost the same as 6074BD with sinc.




@Amy: Feature Requests:

• Do you think it is possible to implement linear interpolation in next firmware/FPGA version, as a user-selectable alternative to sinc?
• Dou you think it would be possible to implement an "average" acquisition mode, like in other models? This would enable smoothing of noisys signals. Since the display is only 320 pixels wide, and since the capture buffer is 3k samples (6k in single channel mode), I guess that averaging up to 8x (or 16x in single-channel model) might be feasible.
• Alternatively to (2) - or additionally - a phosphor emulation would be nice as well. I miss this feature in the PC software as well (also in the PC software for the 6004BD models).
  

gf1

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).

OASJ2YSeeEhBQo1

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.

amy

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.

gf1

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

OASJ2YSeeEhBQo1

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

OASJ2YSeeEhBQo1

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.

gf1

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

gf1

... 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