SDG1025 -Log Sweep Issue? - Page 1
Forum section: electronics / testgear

author: CScott
author_rank: Contributor
timestamp: June 18, 2014, 08:00:08 am
content: Hi AllI'm a newbie here who just got a Siglent SDG1025. I needed to check a filter response and set up a log sweep. The results were far from expected and, according to my measurements at least, the log sweep (i.e logarithmically spaced frequencies) is closer to a quadratic.If you have one of these models SDG10xxx models I would really appreciate if you to do quick check by doing a 2 second log sweep from 1 Hz to 100Kz and reporting back the frequencies at 0, 0.4,0.8, 1.2 1.6 and 2.0 seconds. Here is my dataSDG1025 Log Frequency Sweep ResultsTimeSDG1025 Measured HzExpected Frequency Hz0110.228703.162277660.46490100.61120031.62277660.817100100124600316.2277661.23310010001.4439003162.277661.659800100001.87760031622.77662100000100000Thanks guys,Scotty

author: rf-loop
author_rank: Super Contributor
timestamp: June 18, 2014, 02:18:14 pm
content: Due to many changes (and old log sweep issue also) in FW and bugfixes it is good practice to tell version if find some problem.HW version and FW version from system info screen.

author: CScott
author_rank: Contributor
timestamp: June 18, 2014, 05:00:19 pm
content: Yes, of course:Model SDG1025Boot 11SW 1.01.01.31R1HW 02-00-00-22-26Thanks.

author: CScott
author_rank: Contributor
timestamp: June 19, 2014, 07:34:00 am
content: Anyone? Please? It takes about 5-10 mins to to the test.Thank you!

author: paul
author_rank: Contributor
timestamp: June 21, 2014, 04:15:32 pm
content: I tested my SDG1020 (with firmware version 1.01.01.31)and I get very similar results to you, whether this is log or quadratic is another questionTime Frequency KHz0.2 2.850.4 6.4760.6 11.020.8 16.781.0 24.031.2 33.111.4 44.441.6 58.91.8 77.162.0 100.0BTW it took me longer than 10 minutes to work out how to measure the frequency at set time pointsPaul.

author: rf-loop
author_rank: Super Contributor
timestamp: June 21, 2014, 06:55:16 pm
content: There was old topic (over year ago) where was also handled this log sweep. In this topic there is some more details about it.I have not tested and today my demo SDG1000 is completely disassembled for some special mod so I can not test.But here this old from user "commongrounder"And last message is that log issue is repaired. What is now true, repaired or not?Quote from: commongrounder on April 24, 2013, 04:50:49 pmQuote from: commongrounder on May 14, 2013, 01:23:52 pmQuote from: commongrounder on November 17, 2013, 03:48:30 am

author: paul
author_rank: Contributor
timestamp: June 21, 2014, 10:13:42 pm
content: I plotted the results in a quick graph, as you can see its not what you would expect from a log sweep.Paul.

author: rf-loop
author_rank: Super Contributor
timestamp: June 22, 2014, 09:15:51 am
content: I did not have enough time for better test but I have assembled my demo unit for this test so that I can just barely run it. (also front panel is disassembled)I have not just now test system where I can do simple fast sweep accurate freg count .(just by watching clock, manual trig, watching clock and couter dissplay)Sine outSweepStart: 1000HzStop: 10000HzSweep time 400ssweep: LOGTrig: manualTime point read from from clock by eyes and 4 highest digit from counter (HP53131A)Start 0 sec 1000Hz (real freq 1000.01998xxx)Time point 40sec ~1255Hz (10exp0.1=1259)Time point 80sec ~ 1583Hz (10exp0.2=1585)Time point 200 sec ~3160Hz (10exp0.5 = 3162 )Time point 300 sec ~~5630Hz (10exp0.75=5623)Stop 400 sec 10000HzResult: It can say with enough accurate and confidence that it is 10 base log and nothing else.

author: Bored@Work
author_rank: Super Contributor
timestamp: June 22, 2014, 09:25:06 am
content: Guys, it is still the same issue it was last time. To get a logarithmic horizontal axis displayed on an oscilloscope you need to sweep with the inverse function.https://www.eevblog.com/forum/testgear/siglent-sdg1000-%28aka-lecroy-wavestation%29-firmware-updates/msg222940/#msg222940Strange that the self-styled Siglent/Atten/Gratten "experts" and chills don''t know that by heart.

author: paul
author_rank: Contributor
timestamp: June 28, 2014, 06:12:14 pm
content: I have read through the thread linked to above and it makes sense sort of.So I plotted a simple low pass filter the hard way with a DMM, pen and paper and stepped through from 1KHz to 100KHz and the results are below in LPF Linear sweep.I then changed the frequency scale to LOG and you get the plot shown in Log_Plot attached below.Next do the same thing on the oscilloscope, first with a linear sweep and then with a log sweep, and save the results as gif images attached below.Then overlay the plots onto the screen grabs of the scope (the blue line of the plot is overlaying the yellow trace of the oscilloscope).As you can see the linear plot fits nicely, shouldn't the log plot match ?I am obviously misunderstanding some thing here and demonstrating my ignorance and lack of maths skills, but shouldn't the log plots match ?Paul.

author: CScott
author_rank: Contributor
timestamp: June 30, 2014, 08:10:28 am
content: I got my hands on a second one and repeated the test same result. I spoke with Siglent and they believed this issue had been addressed. It was only after I had tested a second unit that I was able to get them to agree to test for themselves. They said that they will do a firmware update if they can reproduce. I fear there may have been a regression. They were certainly aware that the function is 10**t.BTW, my method was to use a 'scope + delayed trigger and measure cycle time and then tabulate.

author: CScott
author_rank: Contributor
timestamp: June 30, 2014, 08:18:10 am
content: Hi Paul,Quote from: paul on June 28, 2014, 06:12:14 pmThey don't match because the generator is not doing the log sweep correctly. The filter plot shows attenuation greater than the expected at low frequencies as the sweep frequency increases too rapidly.

author: rf-loop
author_rank: Super Contributor
timestamp: June 30, 2014, 11:53:42 am
content: My previous message about short test (and also more data in my hand write test note book) tell that it works just with 10 base log sweep but test sweep frequency range was exactly one decade.With other sweep range width something go wrong in internal math in FW.Siglent need repair this bug in FW, and I believe they do it.

author: paul
author_rank: Contributor
timestamp: June 30, 2014, 12:31:52 pm
content: Hi Scotty,I have plotted your data from the first post in this thread against my own results and they are a close match.Now if you plot this on a log frequency scale, you get strange results (shown below in Log_Plot).However rf-loop`s results plotted with a log frequency scale show a very nice (as expected) straight line. (shown below in rf-loop.png)I agree with rf-loop the only difference I can see is that my plots are over more than one decade.I have double checked and can confirm that it all goes strange if you try and sweep over more than one decade, nice bug !Paul.

author: CScott
author_rank: Contributor
timestamp: June 30, 2014, 03:40:22 pm
content: Just want to give a big thank you to everyone for contributing and running the testsScotty

author: CScott
author_rank: Contributor
timestamp: July 04, 2014, 07:24:38 am
content: Good news. I just got an update from Siglent support 4th July 2014 "We have located the problem. We promise to fix the bug and will release a new version as soon as possible.".Scoty

author: commongrounder
author_rank: Frequent Contributor
timestamp: November 16, 2014, 06:28:52 pm
content: Siglent released a new firmware version a couple of days ago. (.36). Unfortunately, this new version does not appear to correct the log sweep issue (on my SDG1005, anyway), rather the entire sweep mode is now not working correctly. If sweep mode is important to you, I do not recommend updating until this problem is corrected.

author: Mark_O
author_rank: Frequent Contributor
timestamp: November 19, 2014, 05:50:44 pm
content: Quote from: CScott on July 04, 2014, 07:24:38 amQuote from: commongrounderThat update notice should have read,"We promise tofixchange the bug, and will release a newversionbug as soon as possible.".The fact that it took themover 4 monthsto come up with this should be more than a little embarrassing to Siglent.

author: CScott
author_rank: Contributor
timestamp: November 22, 2014, 01:46:23 pm
content: I only just got around to testing this today and I confirmed this does not not fix it at all. I've emailed them again. Give it another four months I guess.I can't see me buying anymore Siglent gear! Very disappointing.

author: Siglent
author_rank: Regular Contributor
timestamp: November 28, 2014, 06:42:22 am
content: Sorry to let you wait so long.we just released a beta version(1.01.01.36R1) to fix the sweep problem, please find it herehttp://www.siglent.com/2014EnglishWebsite/Firmware&Software/Firmware/SDG1000-V100R001B01D01P36R1.rarbelow is the test result of myself.

author: astraios
author_rank: Contributor
timestamp: November 28, 2014, 09:08:46 am
content: Quote from: Siglent on November 28, 2014, 06:42:22 amIt's nice to see you are providing firmware updates.However I think the link you posted is wrong, once I click the Download button, an EasySdm_setup.rar file is downloaded.I can see the new firmware at:http://www.siglent.com/ENs/gjjrj.aspx?id=15By the way, your upgrade instructions (the file Readme.bmp included in the compressed file) are somewhat wrong.They state to insert the USB stick with the firmware and go to the "Firmware Upgrade" option.However the option "Firmware Upgrade" in the utility menu doesn't exist (at least it doesn't exist on my SDG1025).In my case, it was "Update" (on the bottom of the last page, of the utility menu) and once I go there, the Store/Recall button lights up.Then I had to select the firmware file using the file browser and press the Recall function key.After 1-2 minutes, a message appears to inform the user the upgrade finished and to restart the function generator.

author: Siglent
author_rank: Regular Contributor
timestamp: November 28, 2014, 01:05:30 pm
content: Quote from: astraios on November 28, 2014, 09:08:46 amThank you astraios, I need to check the link of siglentamerica, customers can download it from herehttp://www.siglent.com/2014EnglishWebsite/Firmware&Software/Firmware/SDG1000-V100R001B01D01P36R1.rar

author: nctnico
author_rank: Super Contributor
timestamp: November 28, 2014, 03:34:02 pm
content: I just tried and the sweep is working again!

author: commongrounder
author_rank: Frequent Contributor
timestamp: November 28, 2014, 06:39:35 pm
content: I just checked the sweep function as well. Great to see it working again. Plus, the LOG sweep now appears right on and seems to work over any selected frequency range (all the ones I tried, anyway).Don't forget to check out the new selectable impedance on the output level indicator. I tried it with a few different load impedances and the generator calculated the level into those loads pretty accurately. Of course for this to be useful, you really need to know, or discover, the impedance value of your load at the frequencies of interest.This is all with reference to ver .36R1.Thanks to Siglent for taking care of the sweep issue so quickly.

author: toli
author_rank: Frequent Contributor
timestamp: November 28, 2014, 09:05:50 pm
content: just updated my SDG1020 with the same fw. easily done (after reformatting the USB stick to FAT32 instead of NTFS), and seems to work fine so far. log sweep is indeed looking well, and not as it used to be.

author: Macbeth
author_rank: Super Contributor
timestamp: November 28, 2014, 11:12:20 pm
content: Great stuff, Siglent. That was a pretty rapid turnaround!

author: Siglent
author_rank: Regular Contributor
timestamp: December 01, 2014, 09:14:51 am
content: Quote from: Macbeth on November 28, 2014, 11:12:20 pmThank you!

author: nixxon
author_rank: Frequent Contributor
timestamp: December 01, 2014, 08:10:35 pm
content: Quote from: astraios on November 28, 2014, 09:08:46 amIs the procedure still like it was back in February 2013?:(From my posthttps://www.eevblog.com/forum/testgear/siglent-sdg1025-arbitraryfunction-generator-under-some-tests/msg188282/#msg188282)Procedure:0 Turn on the unit and insert a USB-stick with a copy of SDG1000-V100R001B01D01P27.ADS on root level.1 Press <Utility> button2 Select "1/2 ?" (the arrow down character has turned into a question mark)3 Select "Update"4 Highlight the USB stick "USB Device (O:)" (Yellow background)5 Press "Browser/Folder" so it changes to "Browser/File"6 Highlight the update file "SDG100~1.ADS" (Yellow background)7 Select "Recall"Wait 33 seconds for the success messageAfter that I pressed the <Utility> button to exit the menus, pulled out the memory stick and shut the unit off.I booted the unit and confirmed that the Software Version was correct.

author: astraios
author_rank: Contributor
timestamp: December 01, 2014, 08:27:30 pm
content: Quote from: nixxon on December 01, 2014, 08:10:35 pmYes, it's still like that.

author: CScott
author_rank: Contributor
timestamp: January 19, 2015, 10:10:29 am
content: Just in case anyone is interested, I'm STILL waiting for the fixed firmware for this. When I tested 1Hz to 1Mhz it failed.They sent me a 'fixed' version 36R1 back on Nov 28th. When I contacted them they apologized and said to wait for P37. I've had no response now to three emails and it's still P36R1 on the download site. I'm getting pretty ticked off.

author: tautech
author_rank: Super Contributor
timestamp: January 19, 2015, 10:45:37 am
content: Quote from: CScott on January 19, 2015, 10:10:29 amI am and I'll point Siglent to your post.

author: rf-loop
author_rank: Super Contributor
timestamp: January 21, 2015, 03:48:19 pm
content: Quote from: CScott on January 19, 2015, 10:10:29 amCan you explain how it fails? (At this time I do not havre any SDG1000 in stock for test.Last time I fast look just with some start stop values and sweep time it looks like work related to 2013-2014 FW versions where it did not work exept if start stop difference is one decade.Can you give some explanation with data for statement: "it failed"

author: tautech
author_rank: Super Contributor
timestamp: January 21, 2015, 06:17:06 pm
content: Quote from: tautech on January 19, 2015, 10:45:37 amSiglent are looking at your problemCScottCan others back up his claims to add weight for a urgent fix?

author: nctnico
author_rank: Super Contributor
timestamp: January 21, 2015, 06:39:48 pm
content: I just tried it. I used channel1 with a sweep from 1Hz to 1MHz in 1 second. The linear sweep seems fine but a log sweep starts with a low frequency wave of 1Hz but then suddenly jumps to 246Hz after 400ms. If I set the start frequency to 100Hz I get 100Hz for 100ms, 300Hz for 75ms, etc. So the log sweep isn't good. Someone at Siglent needs to ask his/her money back from school regarding the math lessons

author: Lightages
author_rank: Unknown
timestamp: January 21, 2015, 06:48:04 pm
content: Really? Mine is just arriving now in Chile after I purchased one on the assurance on this very forum by one of the experts that the log sweep issue was fixed.......https://www.eevblog.com/forum/testgear/looking-for-reasonable-dds-function-gererator-need-opinions-please/msg577880/#msg577880end of this post......

author: tautech
author_rank: Super Contributor
timestamp: January 21, 2015, 07:10:50 pm
content: Quote from: Lightages on January 21, 2015, 06:48:04 pmCan you too confirm a remaining Log Sweep problem in this thread when you receive it please?

author: rf-loop
author_rank: Super Contributor
timestamp: January 21, 2015, 07:11:50 pm
content: Quote from: nctnico on January 21, 2015, 06:39:48 pmLog sweep from 1Hz to 1MHz in 1 second. omg!How many steps it can produce in this time.... (I have no any idea)But can you check if it follow this table. start 100Hz, stop 1MHz, sweep time 100stime t | frequency0,00 100,005,00 158,4910,00 251,1915,00 398,1120,00 630,9625,00 1000,0030,00 1584,8935,00 2511,8940,00 3981,0745,00 6309,5750,00 10000,0055,00 15848,9360,00 25118,8665,00 39810,7270,00 63095,7375,00 100000,0080,00 158489,3285,00 251188,6490,00 398107,1795,00 630957,34100,00 1000000,00

author: nctnico
author_rank: Super Contributor
timestamp: January 21, 2015, 08:26:57 pm
content: The number of steps doesn't matter. There shouldn't be steps in the signal. The frequency should sweep from the start to the end in one continuous waveform where each frequency flows into the next seemlessly.

author: rf-loop
author_rank: Super Contributor
timestamp: January 22, 2015, 05:20:24 am
content: Quote from: nctnico on January 21, 2015, 08:26:57 pmIt was todays best joke at this morning.

author: nctnico
author_rank: Super Contributor
timestamp: January 22, 2015, 08:16:55 am
content: A signal generator which outputs a sweep in steps is useless. Imagine working on a narrow filter. If the filter's frequency of interest is between 2 steps then you won't be able to see the filter's frequency response. That is why a sweep should include all frequencies.You are probably confusing RF generators; these are a special case Because of their construction they can't output a continious sweep (so they usually have steps and a configurable dwell time) but an arbitrary waveform generator like the SDG1000 should have no problem. The linear sweep works OK so the log sweep still suffers from a bug.

author: rf-loop
author_rank: Super Contributor
timestamp: January 22, 2015, 08:58:07 am
content: Quote from: nctnico on January 22, 2015, 08:16:55 amI have asked if someone can test run SDG1000 and check if it pass with table I previously made.(this table do NOT mean it steps just with these steps but frequencies need be as table in given time points.It is also good to remember that it is not analog sweeper.Sidenote: If equipment do not work as we dream or imagine it do not mean it have always bug, we perhaps have only finded equipment limits. (I do not know yet enough about this case so I do not claim it is ok or there is bug. Also it is interesting question what is not working, what is working and what is bug and what is natural feature due to equipment working priciple and circuit. User need know his equipments and its limits.If I check narrow filter, I really do not use 1Hz to 1MHz sweep span with 1s sweep time.With narrow filter need use enough narrow and/or also also enough slow sweep. We all know why.

author: nctnico
author_rank: Super Contributor
timestamp: January 22, 2015, 09:13:20 am
content: With small or wide sweep spans the argument against steps still holds. If a filter's response is in between 2 steps then you'll miss it entirely or get the wrong results. In the frequency domain a sweep should show a flat line between the start and stop frequencies. Not a collection of single 'peaks'.

author: rf-loop
author_rank: Super Contributor
timestamp: January 22, 2015, 09:26:02 am
content: Quote from: nctnico on January 22, 2015, 09:13:20 amOf course basic fundamentals are true also here.

author: toli
author_rank: Frequent Contributor
timestamp: January 23, 2015, 08:37:32 am
content: I verified this is indeed the case with my SDG1020 as well. I though the problem was fixed as it looked like the sweep is logarithmic at first sight, and I didn't look closer. But now that I have, it does have these steps in frequency which makes it quite stupid. I've never used an instrument that suffers from this issue, be it analog or digital function gens.I do hope this will be fixed, at the very least, the number of steps should be so high, that even high Q filters won't be missed by the sweep.

author: Lightages
author_rank: Unknown
timestamp: January 23, 2015, 03:07:35 pm
content: Well I am very disappointed. I asked which generator to buy and was told in the thread by one of the experts that log sweep was fixed. I made my purchase decision on this recommendation because I want log sweep. If it isn't really fixed then it goes back and I have wasted some tme and will lose money on the return shipping.I have been wary of trying Siglent, and now I have justification. I don't think I will bother with any Siglent equipment again if they can't fix things correctly.

author: Unknown
author_rank: Unknown
timestamp: January 23, 2015, 04:14:06 pm
content: In a digital synthesized generator (like the SDG1025 and most others on the market), the circuitry is based on a precision local oscillator (LO) that is often 10 MHz. In the "old days" the oscillator was controlled by a DC voltage or some other means. For large frequency range changing the oscillator might have had a "Range" knob which then selected a different capacitor or resistor, for example. This would have been considered an "analog generator". In order to sweep it, all we had to do was to change that analog control voltage to a linear or logarithmic ramp and now we had a true analog sweep.Nowadays, with DDS circuitry, it is normally not possible to truly sweep the LO in a true analog fashion. The frequency is adjustable in "steps". When we sweep a DDS generator, we are telling the unit to, in essence, automatically change it's frequency from the Start frequency to the Stop frequency over time. Since the only way a DDS can do this is by changing some logic functions (multipliers and dividers) it must sweep using steps. The question of how many steps it takes to do so is determined by the design. This would be true both for linear and logarithmic sweeps.I don't know offhand the number of steps the SDG1025 takes between two points. It may depend on the sweep range and speed time, but it might not.If one is testing a sharp filter and doesn't want to miss any frequency resolution I would recommend sweeping slowly and over as narrow of a range as possible. We want to sweep slowly so that the filter has time to react. The sharper the skirts on the filter, the slower we need to sweep in order to give it time to respond.We would want to sweep over as narrow a range as possible when testing narrow filters or sharp skirts in order to make our sweep step sizes as small as possible. Let's say, for a hypothetical example, that we have 1000 sweep step points available (I don't have the number of steps available for a SDG1025 but can get that for you). If we sweep from 1 MHz to 11 MHz that is a range of 10 MHz. If we now divide 10 MHz by 1000 steps we get a step size of 10 KHz (again, I don't know offhand how many steps this model has). But if we were to sweep from say, 5.50 MHz to 5.55 MHz we now have a sweep range of .05 MHz (500 KHz). Dividing 500K by 1000 steps we now get a step size of 50 Hz. Much better frequency resolution.This is harder to calculate in log sweep mode because the sweep is no longer linear but constantly changing. Again, we can get you a more detailed answer than I am giving.While there are other ways to get around this step issue found in DDS generators, the complexity and design becomes much greater. Some older or lower cost generators might have a digital display but are actually analog generators. What the digital display is doing is it is actually counting the generator frequency. An easy way to tell if this is the case is 1) They usually have fewer digits and less resolution. 2) They don't respond instantaneously to changing the frequency on the unit. It takes a moment to actually "count" the signal.3) They will probably drift over time. So it might look like a digital generator but it is actually not.I hope this helps.Steve

author: nctnico
author_rank: Super Contributor
timestamp: January 23, 2015, 05:04:06 pm
content: Actually it's not difficult to create a DDS with a continuous adjustable frequency range. The biggest trick is to update the divider at the right moment. My guess it that the linear sweep is done inside the FPGA but the log sweep is done by software. IMHO it would be better when Siglent removes the log sweep or fixes it. Personally I could do without the log sweep as long as the linear sweep works.

author: rf-loop
author_rank: Super Contributor
timestamp: January 23, 2015, 05:05:26 pm
content: We do not know how it work. Also there is claimds that still it do not work right. But we do not have real accurate data about these claims. I have asked someone do slow sweep and check with my table if even frequencies in some time points atre correct in LOG mode. But only words that it do not work.What is sweep.How Agilent can put to datasheet (yes this is ancient but still, there reads in aaddvertise and in data sheet only that it have LOG and LIN sweep. Do they lie? No. But user need know his equipment and use it with its limitations.Agilent with full satisfaction and happy write LOG and LIN sweep and sweeping time starting from 1ms and up to really long time. And frequency limits just what are this generator min and max.What is this, can it do 1Hz to 10MHz log continuous sweep without stepping. They promise there is LOG and LIN sweep.(I do not have this model so I have not tried and this is not interesting at all but... who tell to Agilent that this unit LOG sweep do not work right?)Then after read some more information (for Siglent this kind of information is not available)Omg, it is stepping. And it is Agilent DDS Arb (but old design, aka simple machines - as also Siglent is. Cheap and working principle is simple.)Someone told have never seen DDS Arb gen stepping.This lot of used well known Agilent older model is stepping.Some collection of knowledge about Agilent 33120A:QuoteWhat now?We need know how this SDG1000 series work.Priority 1. We need first know if it calculate LOG right or wrong.THIS was previously named issue.Wrong math. nd this they promise fix. (I have believed they have fixed it but previousluy I did only extremely fast check with some 4-5 time points and what I find it was nearly like ok and also over one decade. Old version did right math only with one decade in freq) We need now first know if THIS math is really repaired or not. And there is table what who ever SDH1000 owner can use for check if math is now correct.After then:Totally other case is solve or get information how it really works and steps or what ever it is doing? If user know how it works then can think if there is possible bug or not. Or if it can develop better just with some FW trick. But also, if user know better his equipment he perhaps can use it better for his needs with equipment limitations.

author: nctnico
author_rank: Super Contributor
timestamp: January 23, 2015, 05:15:04 pm
content: Quote from: rf-loop on January 23, 2015, 05:05:26 pmSorry but several people including me already verified that the log sweep mode produces a signal which isn't a continuously increasing frequency but steps. That is a no-go so no need to look any further. Just accept that (or get a unit to test it yourself).

author: rf-loop
author_rank: Super Contributor
timestamp: January 23, 2015, 06:31:30 pm
content: Quote from: nctnico on January 23, 2015, 05:15:04 pmI know it is stepping, this I have seen when I first time look SDG1000. This have not been question at all when LOG sweep was reported problem. There was somehow wrong math together with 1 decade limit. After then Siglent promise repair it. Now they have puplished fixed FW and now you tell this problem is not at all important but LOG sweep fails because it is stepping and useless because 1 second LOG sweep from 1Hz to 1MHz do not work with continuously changing frequency without steppping.I hope they can change this stepping details (and also add limits to FW so that it restrict user select settings what it can not then do) but I have strong feeling that there is not at all enough resources in this HW to do "stepless" continuous and fast wide range log sweep.With narrow filters least I use also narrow sweep (and also enough slow sweep due to basic fundamentals of filters functions. I really do not try sweep over 100Hz filter pb in 100us or 1ms if I want know something about it.

author: Lightages
author_rank: Unknown
timestamp: January 23, 2015, 06:38:35 pm
content: LOL, 1Hz to 1MHz in 1 sec? That is the complaint? That this doesn't work properly? Sorry but no generator can do that properly, analog or not. I will see how mine performs with rational use when I get it next week.

author: commongrounder
author_rank: Frequent Contributor
timestamp: January 23, 2015, 06:51:35 pm
content: I have come late to this discussion, but own a SDG1005 and have a great deal of interest in the log sweep function, since I use it extensively in my audio work. I do honestly believe the last firmware revision basically fixed the PROFILE of the log sweep, but may have a limitation in the stepping of frequencies over long ranges. The most important thing I want to say to Siglent is DO NOT remove the sweep function as it stands from the firmware!!! When used over reasonable frequency ranges and sweep rates it does track correctly and the steps are fine enough (Iwouldbe interested to know how many steps are used in a sweep and if that changes with sweep length, etc.)ToRF-LOOP: I did run the 100hz to 1mhz 100 second sweep and the tracking was correct. The log function works. What I observed is at the low end the steps are stretched out, then steadily increase in speed as the sweep progresses. This would indicate that in log mode, the step spacing is recalculated using the log function, a logical way to achieve the tracking. The issue is there is not enough resolution to keep the steps invisible. There should be interpolation of points to fill in and smooth out the sweep at the "bottom" end. The big question is if the hardware has the ability, with a change in firmware, to accomplish this. Remember folks, this is a roughly $300 USD device. Unthinkable, even just a few years ago to have an AWG in this price range. I am going to keep my opinions to myself about the usefulness of a 1hz to 1mhz 1 second log sweep.

author: rf-loop
author_rank: Super Contributor
timestamp: January 23, 2015, 08:00:46 pm
content: Quote from: commongrounder on January 23, 2015, 06:51:35 pmThank you about this information. Specially this underlined push me to thinking if it still can do some amount more optimized by FW.... It looks like In need agen buy one SDG1000 for my own use just for do some investigations how it really works. Also nice to know that we can now override LOG math mistake. Now can concentrate to look if this stepping is ok or if there is some stupidity.Some times I feel that some FW programmes (not pointed to any individual company alone) do not so much know about how these equipments are normally used in real work or hobby.

author: nctnico
author_rank: Super Contributor
timestamp: January 23, 2015, 08:08:32 pm
content: Quote from: Lightages on January 23, 2015, 06:38:35 pmOfcourse it is possible. You just won't get much of a 1Hz cycle. OTOH that is exactly what the SDG1000 is doing for about 400ms!

author: Lightages
author_rank: Unknown
timestamp: January 23, 2015, 08:12:09 pm
content: No, you can't produce anything useful in a sweep from 1Hz to 1MHz in 1 second. It will give you nonsense.

author: nctnico
author_rank: Super Contributor
timestamp: January 23, 2015, 08:17:40 pm
content: You can't tell whether a signal is useful to someone or not. The generator supports it so it should do it properly. Back to the topic: IMHO stepping a sweep is just wrong because it is no longer a sweep.edit:I did some further testing: It seems the problem is driven by the frequency range of the log sweep. If I let it sweep from 10kHz to 1MHz it doesn't matter whether I select 1 second or 10 seconds sweep time. The frequency stepping happens with the same number of steps.