Poll

What is your interest in the Hantek DDS 3x25?

I own one
36 (27.1%)
I am considering getting one
40 (30.1%)
Curious about the hack
16 (12%)
Just passing through
41 (30.8%)

Total Members Voted: 111

Author Topic: Review: Hantek DDS 3X25. Anyone own one?  (Read 289877 times)

0 Members and 1 Guest are viewing this topic.

Offline torch

  • Frequent Contributor
  • **
  • Posts: 397
Re: Review: Hantek DDS 3X25. Anyone own one?
« Reply #425 on: December 16, 2012, 03:37:45 am »
Isn't the replacement missing about 3 BNC connectors for $100 more? I have to confess that I kind of lost interest after that...
 

Offline saturationTopic starter

  • Super Contributor
  • ***
  • Posts: 4787
  • Country: us
  • Doveryai, no proveryai
    • NIST
Re: Review: Hantek DDS 3X25. Anyone own one?
« Reply #426 on: December 16, 2012, 03:08:09 pm »
mecha and you guys have certainly taken the 3x25 much farther than Hantek could have envisioned, I would suspect this is the reason its been resurrected, it shouldn't have been canceled in the first place, maybe the g in the name 1025G is for Goltek  :-+?

Checking just now this vendor sells the new version for ~ price as any new 3x25 now remaining on eBay:

http://www.circuitspecialists.com/hantek-1025g.html

The photos, description, software, specs and accessories are ~  identical to the 3x25.


I can't understand why Hantek seems to have orphaned the DDS 3X25.
Well, as mentioned in the other thread I recently started, they are producing more of them - just putting them in a slicker-looking container - and asking a lot more money for them ($231 at AliExpress).  So they are trying to cash in on the success of the DDS-3X25 - but without any real extra effort on their part.
Best Wishes,

 Saturation
 

Offline T4P

  • Super Contributor
  • ***
  • Posts: 3697
  • Country: sg
    • T4P
Re: Review: Hantek DDS 3X25. Anyone own one?
« Reply #427 on: December 16, 2012, 04:34:54 pm »
Think hantek wants to give it new look to match the other USB oscilloscopes but you know what? Most aliexpress sellers will probably always jack up the price
On taobao from the same seller the price delta between the 2 is about 15USD
« Last Edit: December 16, 2012, 04:37:35 pm by T4P »
 

Offline PuterGeek

  • Regular Contributor
  • *
  • Posts: 88
  • Country: us
    • SolutionsPLUS engineering
Re: Review: Hantek DDS 3X25. Anyone own one?
« Reply #428 on: December 17, 2012, 12:10:31 am »
...freq change at zero crossing is one thing, signal sweep "flatness" is another, that can be a challenge since ds3x25 is not flat at >5MHz...

One of my many 'plans' is to mode mine with a different DC-DC switcher and a 5th order LC output filter.

The op amp they used is pretty good but they only used a +/- 5V DC-DC converter. If we changed that to a +/- 12V switcher it would have greater output, especially into a 50 ohm load. There are numerous pin compatible op-amps that could be used also.

The simple one capacitor 'filter' on the DAC output won't be anywhere close to flat. 'Real' DDS have a passive LC filter on the output that is pretty flat up to the cutoff frequency and then rolls off very steeply. A small PCB with the filter should be easy to embedded since the parts are small.

Maybe I'll whip up a schematic to share in case someone wants to try my idea. What would be a good cutoff frequency do you think I should use?
 

Offline Mechatrommer

  • Super Contributor
  • ***
  • Posts: 11714
  • Country: my
  • reassessing directives...
Re: Review: Hantek DDS 3X25. Anyone own one?
« Reply #429 on: December 17, 2012, 12:32:17 am »
What would be a good cutoff frequency do you think I should use?
100 or 200MHz?

Maybe I'll whip up a schematic to share in case someone wants to try my idea.
yes please do. i will be interested. ;)
Nature: Evolution and the Illusion of Randomness (Stephen L. Talbott): Its now indisputable that... organisms “expertise” contextualizes its genome, and its nonsense to say that these powers are under the control of the genome being contextualized - Barbara McClintock
 

Offline torch

  • Frequent Contributor
  • **
  • Posts: 397
Re: Review: Hantek DDS 3X25. Anyone own one?
« Reply #430 on: December 17, 2012, 12:39:55 am »
maybe the g in the name 1025G is for Goltek 

It should be for Goltek. However, I think it stands for "Gone" -- as in: "Were did the other 3 BNC jacks go? They're Gone."
 

Offline Mechatrommer

  • Super Contributor
  • ***
  • Posts: 11714
  • Country: my
  • reassessing directives...
Re: Review: Hantek DDS 3X25. Anyone own one?
« Reply #431 on: December 17, 2012, 02:47:33 am »
maybe the g in the name 1025G is for Goltek 
It should be for Goltek. However, I think it stands for "Gone" -- as in: "Were did the other 3 BNC jacks go? They're Gone."
its even match my 10x25 amplifier name... http://www.soasystem.com/eng/goltek/amplifier.htm i should file a "trademark name infringement" 8) but their 1025 still use ±3V, bugger! so i vote "G" is for buGger. i dont believe its for Goltek since Rigol name is embedded in it and i dont believe they are both friend.
Nature: Evolution and the Illusion of Randomness (Stephen L. Talbott): Its now indisputable that... organisms “expertise” contextualizes its genome, and its nonsense to say that these powers are under the control of the genome being contextualized - Barbara McClintock
 

Offline zibadun

  • Regular Contributor
  • *
  • Posts: 112
  • Country: us
Re: Review: Hantek DDS 3X25. Anyone own one?
« Reply #432 on: December 17, 2012, 06:04:10 am »
edit: added DDSDownload times: I almost fell asleep scanning a 30 MHz range with a 50khZ step.  that DDSDownload call takes forever  :=\  :=\     Anybody figured out how to make a faster frequency change? 

freq pts periods elapsed time (secs)
1000000 4000 20 0.509
1052631 3990 21 0.509
1104972 3982 22 0.512
1156069 3979 23 0.509
1204819 3984 24 0.510
1250000 4000 25 0.508
1307189 3978 26 0.510
1351351 3996 27 0.509
1408450 3976 28 0.510
1459854 3973 29 0.510
1503759 3990 30 0.524
1550387 3999 31 0.509
1600000 4000 32 0.509
1652892 3993 33 0.509
1709401 4095 35 0.518
1754385 3990 35 0.509
1801801 3996 36 0.509
1851851 3996 37 0.509
1904761 4095 39 0.517
1960784 4080 40 0.517

Is this a normal  delay or am I doing something wrong?   At this rate it takes five minutes to do a 30mhz sweep
« Last Edit: December 17, 2012, 12:50:31 pm by zibadun »
 

Offline marmad

  • Super Contributor
  • ***
  • Posts: 2979
  • Country: aq
    • DaysAlive
Re: Review: Hantek DDS 3X25. Anyone own one?
« Reply #433 on: December 17, 2012, 03:06:55 pm »
edit: added DDSDownload times: I almost fell asleep scanning a 30 MHz range with a 50khZ step.  that DDSDownload call takes forever  :=\  :=\     Anybody figured out how to make a faster frequency change?
Look at this old post of mine. I think it explains what you're looking for - and can point you in the right direction. Let me know if you need more.

Edit: This post might help you as well.
« Last Edit: December 17, 2012, 03:21:58 pm by marmad »
 

Offline zibadun

  • Regular Contributor
  • *
  • Posts: 112
  • Country: us
Re: Review: Hantek DDS 3X25. Anyone own one?
« Reply #434 on: December 17, 2012, 10:10:57 pm »

Look at this old post of mine. I think it explains what you're looking for - and can point you in the right direction. Let me know if you need more.

Edit: This post might help you as well.

Thanks, I think I understand the formulas and arithmetic behind them. But  I don't see how I can avoid downloading a new waveform every time I need to change the frequency.  Even if I'm just changing the number of points with the same wave buffer don't I still need to call DDSDownload?   It seems transfering of the buffer takes up most time.   May be I will try with the minimum number of points and periods that will give the desired frequency and save on the transfer time a bit.

I guess an easier question to ask is  - can *any* software that was developed so far do a 600 step sweep starting at 1 mhz, lets say, in under a minute?  No constrains on the frequency or glitch free sweep, as long as steps are more or less evenly spaced. 
« Last Edit: December 17, 2012, 10:14:01 pm by zibadun »
 

Offline marmad

  • Super Contributor
  • ***
  • Posts: 2979
  • Country: aq
    • DaysAlive
Re: Review: Hantek DDS 3X25. Anyone own one?
« Reply #435 on: December 17, 2012, 10:36:52 pm »
Thanks, I think I understand the formulas and arithmetic behind them. But  I don't see how I can avoid downloading a new waveform every time I need to change the frequency.  Even if I'm just changing the number of points with the same wave buffer don't I still need to call DDSDownload?   It seems transfering of the buffer takes up most time.   May be I will try with the minimum number of points and periods that will give the desired frequency and save on the transfer time a bit.

I don't think you're getting the formulas. Once you've downloaded a waveform, you can change the frequency by using the DDSSetFrequency command, as noted in the code at the bottom of the post from the second link. But without using the DDSDownload command, you're going to be limited to what frequencies you'll be able to get (as noted in those posts). And because the Hantek uses a clock divider - the number of frequencies you can hit by just changing the clock rate (without downloading) gets smaller as you get closer to the maximum DAC clock of 200MHz - it's just a function of math.

As far as speed goes, the speed at which you can change the frequency will be limited by your interface/software/OS/computer. If you want to do 600 steps in a minute, that means 10ms 100ms per step - which would probably be close to the maximum. I think I was able to get that speed with tests I ran. The Hantek software accomplishes sweeps with faster speeds - but they're definitely using commands that they haven't documented to the general public (plus they don't allow sweeps above 100kHz). Boy, I need food :D It's easy to get that speed!
« Last Edit: December 17, 2012, 11:01:37 pm by marmad »
 

Offline torch

  • Frequent Contributor
  • **
  • Posts: 397
Re: Review: Hantek DDS 3X25. Anyone own one?
« Reply #436 on: December 17, 2012, 10:44:59 pm »
Using Goltek, I set the start at 1Mhz, the end for 30Mhz, step at 50Khz, interval at 1ms and single-cycle. I hit "run" and the stopwatch at the same time. 15 seconds to complete one cycle -- on the laptop with USB2. On the older slower laptop with USB1.1, the identical setup took 1 minute, 55 seconds.

 

Offline marmad

  • Super Contributor
  • ***
  • Posts: 2979
  • Country: aq
    • DaysAlive
Re: Review: Hantek DDS 3X25. Anyone own one?
« Reply #437 on: December 17, 2012, 10:49:50 pm »
Using Goltek, I set the start at 1Mhz, the end for 30Mhz, step at 50Khz, interval at 1ms and single-cycle. I hit "run" and the stopwatch at the same time. 15 seconds to complete one cycle -- on the laptop with USB2.

That's ~25.8ms per step.

Edit: Clearly my brain needs food (I've delayed my dinner) - my post above was wrong by a factor of 10 :o He needs 100ms per step, duh - so well within reach by Goltek or any software.
« Last Edit: December 17, 2012, 11:02:40 pm by marmad »
 

Offline marmad

  • Super Contributor
  • ***
  • Posts: 2979
  • Country: aq
    • DaysAlive
Re: Review: Hantek DDS 3X25. Anyone own one?
« Reply #438 on: December 17, 2012, 11:41:22 pm »
Here's an image showing a big problem with sweeping with the Hantek.

The image shows the frequency change point from 200Hz to 300Hz - but because the frequency doesn't change at the zero-crossing of the waveform, you get a spurious frequency injected - in this case, it happens to be ~287Hz - as shown in the cursor measurement window.

Edit: BTW, I was incorrect in what I posted in a previous message. I did some more testing and it turns out that the Hantek software isn't capable of doing smooth sweeps either. Honestly, with the various problems inherent in the device (no zero-crossing of frequency change, no sync signal for sweep, etc, etc) I really don't think it's a good thing to use for sweeping - especially above 5MHz - but perfectly fine for basic signals and simple arbitrary patterns.
« Last Edit: December 18, 2012, 12:15:06 am by marmad »
 

Offline zibadun

  • Regular Contributor
  • *
  • Posts: 112
  • Country: us
Re: Review: Hantek DDS 3X25. Anyone own one?
« Reply #439 on: December 18, 2012, 02:05:58 am »
Using Goltek, I set the start at 1Mhz, the end for 30Mhz, step at 50Khz, interval at 1ms and single-cycle. I hit "run" and the stopwatch at the same time. 15 seconds to complete one cycle -- on the laptop with USB2. On the older slower laptop with USB1.1, the identical setup took 1 minute, 55 seconds.

thanks for the stopwatch test torch. wow something is really wrong with my setup. The same scan took over five minutes here.  I'd be happy with 15 secs. 

update:  looks like a bad port/hub on my pc.  i switched the cable to another port and got 50ms instead of 500 to switch frequencies.  32 seconds on goltek.  Not as good as 15 but much better than before!  hmm I thought usb port is a usb port ;)

The image shows the frequency change point from 200Hz to 300Hz - but because the frequency doesn't change at the zero-crossing of the waveform, you get a spurious frequency injected - in this case, it happens to be ~287Hz - as shown in the cursor measurement window.

Edit: BTW, I was incorrect in what I posted in a previous message. I did some more testing and it turns out that the Hantek software isn't capable of doing smooth sweeps either. Honestly, with the various problems inherent in the device (no zero-crossing of frequency change, no sync signal for sweep, etc, etc) I really don't think it's a good thing to use for sweeping - especially above 5MHz - but perfectly fine for basic signals and simple arbitrary patterns.

isn't this a transition problem? like a DDS settle time which equals some N number of samples.  I've seen this in a digital mixer in another device. every time you retune the mixer there was all kinds of garbage injected to the signal,but it lastsed only a few clock cycles.  It may even be specified in the datasheet..  In some cases you may be able to account for that transition in whatever is on the "receiving" end of the sweep..  At least that is what I'm hoping to do in my project...


« Last Edit: December 18, 2012, 03:45:29 am by zibadun »
 

Offline marmad

  • Super Contributor
  • ***
  • Posts: 2979
  • Country: aq
    • DaysAlive
Re: Review: Hantek DDS 3X25. Anyone own one?
« Reply #440 on: December 18, 2012, 03:00:50 am »
isn't this a transition problem? like a DDS settle time which equals some N number of samples.  I've seen this in a digital mixer in another device. every time you retune the mixer there was all kinds of garbage injected to the signal,but it lastsed only a few clock cycles.  It may even be specified in the datasheet..  In some cases you may be able to account for that transition in whatever is on the "receiving" end of the sweep..  At least that is what I'm hoping to do in my project...

I don't think so. I think it's a limitation of the hardware design or bad firmware implementation. If you use DDSDownload to change frequencies on the fly, you get large glitches in the output - where the waveform vanishes then reappears while the new sample memory is being loaded. If you use DDSSetFrequency to change frequencies on the fly, you don't get the big glitches - but the firmware just appears to change the clock frequency as soon as it receives the command (instead of waiting for the zero-crossing / beginning of sample memory) because the frequency 'shift' does not appear to be regular. If you look carefully at sweeps, you see the 'shift' happen at different points on the waveform. I don't have another sweep generator to test against (yet) but I think a properly designed and programmed one would be able to make frequency changes that would be smooth (or at least with the exact same shift at every changeover).
 

Offline torch

  • Frequent Contributor
  • **
  • Posts: 397
Re: Review: Hantek DDS 3X25. Anyone own one?
« Reply #441 on: December 18, 2012, 04:04:58 am »
- but the firmware just appears to change the clock frequency as soon as it receives the command (instead of waiting for the zero-crossing / beginning of sample memory) because the frequency 'shift' does not appear to be regular. If you look carefully at sweeps, you see the 'shift' happen at different points on the waveform. I don't have another sweep generator to test against (yet) but I think a properly designed and programmed one would be able to make frequency changes that would be smooth (or at least with the exact same shift at every changeover).

So the randomness is introduced by the timing of the instruction from the computer. I wonder if there could be a hardware work-around? Either through the microprocessor control interface or perhaps some sort of USB buffer controlled by the sync output of the Hantek.

Maybe something even simpler: connect the sync out to the trigger in, send the first waveform and turn on "ext trig mode". Would the Hantek then wait for it's own signal falling signal before starting the next frequency change?
 

Offline torch

  • Frequent Contributor
  • **
  • Posts: 397
Re: Review: Hantek DDS 3X25. Anyone own one?
« Reply #442 on: December 18, 2012, 07:27:29 am »
So much for the simple cable between sync and trigger -- it only works randomly.
 

Offline zibadun

  • Regular Contributor
  • *
  • Posts: 112
  • Country: us
Re: Review: Hantek DDS 3X25. Anyone own one?
« Reply #443 on: December 19, 2012, 12:13:39 am »
got something semi-useful out of the generator in the 1-30mhz sweep.   attached is a couple of filter responses (aka bode plots) made with the help of hantek... (don't laugh  :-DD)

I also noticed the DDSDownload function will randomly fail to change the frequency and needs to be retried.
 

Offline PuterGeek

  • Regular Contributor
  • *
  • Posts: 88
  • Country: us
    • SolutionsPLUS engineering
Re: Review: Hantek DDS 3X25. Anyone own one?
« Reply #444 on: December 19, 2012, 06:55:18 am »
What would be a good cutoff frequency do you think I should use?
100 or 200MHz?

Maybe I'll whip up a schematic to share in case someone wants to try my idea.
yes please do. i will be interested. ;)

It is going to require a Bessel filter and will need to be more than 5 poles to get good results. I will need to run a simulation to verify some things and may need to probe around with my scope too.

Not sure I will have this done before New Year because of the holidays but I am working on it.
 

Offline zibadun

  • Regular Contributor
  • *
  • Posts: 112
  • Country: us
Re: Review: Hantek DDS 3X25. Anyone own one?
« Reply #445 on: December 23, 2012, 04:00:33 pm »
What would be a good cutoff frequency do you think I should use?
100 or 200MHz?

Maybe I'll whip up a schematic to share in case someone wants to try my idea.
yes please do. i will be interested. ;)

It is going to require a Bessel filter and will need to be more than 5 poles to get good results. I will need to run a simulation to verify some things and may need to probe around with my scope too.

Not sure I will have this done before New Year because of the holidays but I am working on it.

I'd vote for 100 MHz or even 30 MHz cutoff frequency.  The "sine" wave spectrum does not look very clean to me at HF (over 5-10 mhz). May be a good low pass filter will help with this. 
 

Offline PuterGeek

  • Regular Contributor
  • *
  • Posts: 88
  • Country: us
    • SolutionsPLUS engineering
Re: Review: Hantek DDS 3X25. Anyone own one?
« Reply #446 on: December 23, 2012, 04:34:35 pm »

I'd vote for 100 MHz or even 30 MHz cutoff frequency.  The "sine" wave spectrum does not look very clean to me at HF (over 5-10 mhz). May be a good low pass filter will help with this.

The filter will necessarily be a compromise. The maximum usable output would be about 80 MHz (40% of 200 MHz sample clock). If we only wanted sine waves we could use a 7 pole elliptical filter with quick falloff and get good results. But the elliptical filter phase delay and impulse response are horrible for arbitrary waveforms.

A Bessel filter is usable but rolls off very slowly so it requires a lot of poles (9 or more). I'll try to post some simulation output later.

p.s. I am a EE but not a filtering expert. This is based on my research on filtering AWGs.
 

alm

  • Guest
Re: Review: Hantek DDS 3X25. Anyone own one?
« Reply #447 on: December 23, 2012, 04:52:39 pm »
Some AWGs use a different filter for sine output than for other signals.
 

Offline PuterGeek

  • Regular Contributor
  • *
  • Posts: 88
  • Country: us
    • SolutionsPLUS engineering
Re: Review: Hantek DDS 3X25. Anyone own one?
« Reply #448 on: December 23, 2012, 07:52:26 pm »
Some AWGs use a different filter for sine output than for other signals.

That would be possible but would be a more difficult mod to include inside the enclosure which was my goal. One way to do that would be to change the frequency counter input to a second output.

An alternative would be external filters which is less appealing to me.
 

Offline Mechatrommer

  • Super Contributor
  • ***
  • Posts: 11714
  • Country: my
  • reassessing directives...
Re: Review: Hantek DDS 3X25. Anyone own one?
« Reply #449 on: December 23, 2012, 09:41:23 pm »
there's plenty of room in the ds3x25, maybe you can use relay or something and switch to change the filter instead of providing 2 separate and simultaneous output. btw, i will love to further modify my ds3x25, but i already have entirely different plan for this "arbitrary wave generator project", the only problem is "Time".
Nature: Evolution and the Illusion of Randomness (Stephen L. Talbott): Its now indisputable that... organisms “expertise” contextualizes its genome, and its nonsense to say that these powers are under the control of the genome being contextualized - Barbara McClintock
 


Share me

Digg  Facebook  SlashDot  Delicious  Technorati  Twitter  Google  Yahoo
Smf