Which scope below $300 has best. FFT function - Page 1
Forum section: electronics / testgear

author: gfmucci
author_rank: Regular Contributor
timestamp: May 31, 2020, 08:05:13 pm
content: Which scope below $300 has best FFT function? How important is bit memory/record length to the quality of this function compared to other specs?

author: nctnico
author_rank: Super Contributor
timestamp: May 31, 2020, 08:46:55 pm
content: That is the Analog discovery.FFT length is important to get a high frequency resolution. More bits means more dynamic range.

author: Fungus
author_rank: Super Contributor
timestamp: May 31, 2020, 10:47:02 pm
content: Quote from: nctnico on May 31, 2020, 08:46:55 pmAnalog Discovery2.

author: egonotto
author_rank: Super Contributor
timestamp: May 31, 2020, 10:56:23 pm
content: Quote from: nctnico on May 31, 2020, 08:46:55 pmHello,more FFT length give also more dynamic range.Best regardsegonotto

author: nctnico
author_rank: Super Contributor
timestamp: May 31, 2020, 11:05:12 pm
content: Quote from: egonotto on May 31, 2020, 10:56:23 pmNo. You'll always be limited by the number of bits in order to resolve the signal.

author: Wolfgang
author_rank: Super Contributor
timestamp: June 01, 2020, 12:05:12 am
content: Quote from: gfmucci on May 31, 2020, 08:05:13 pmThe budget scopes like Rigol or Siglent are lousy.Most important is resolution, because that limits your dynamic range.What I do is sample the tracks into a PC via SCPI and do the FFT there. MUCH better and flexible.Expensive scopes with a 16bit resolution mode (oversampling plus averaging) create a good FFT, normally (Keysight Infiniium, e.g.).

author: rsjsouza
author_rank: Super Contributor
timestamp: June 01, 2020, 12:51:11 am
content: Quote from: gfmucci on May 31, 2020, 08:05:13 pmWhat is the use? If audio, then a soundcard could go a very long way and do a much better job than any real oscilloscope.

author: Elasia
author_rank: Frequent Contributor
timestamp: June 01, 2020, 01:16:34 am
content: Quote from: Wolfgang on June 01, 2020, 12:05:12 amI've been doing this method for years although its usually for just spitting out the occasional fancy graph for an exec lolSomething like matlab will run numbers around most scopes.. it just needs the data

author: TK
author_rank: Super Contributor
timestamp: June 01, 2020, 04:23:18 am
content: You can get the GW Instek GDS1054B for $310 at tequipment. I think it has a very decent FFT. Can be hacked to over 100MHz.

author: egonotto
author_rank: Super Contributor
timestamp: June 01, 2020, 05:10:10 am
content: Quote from: nctnico on May 31, 2020, 11:05:12 pmHello,but increasing the measurement period and the number of samples by a factor of 10reduces the bin size with that factor and lowers the noise floor by 10 dBBest regards

author: _Wim_
author_rank: Super Contributor
timestamp: June 01, 2020, 06:11:51 am
content: Quote from: Fungus on May 31, 2020, 10:47:02 pmFor FFT (and almost every other spec apart from power supplies) the original discovery has the same specs as version 2, but the original one can often be bought on Ebay for less than 100$, which makes it an absolute bargain for the functionality is offers.

author: tautech
author_rank: Super Contributor
timestamp: June 01, 2020, 09:10:04 am
content: Some examples of SDS1202X-E FFT experiments from a few months back:https://www.eevblog.com/forum/beginners/is-this-oscilloscope-perhaps-the-best-for-the-beginner/msg2985420/#msg2985420And more earlier in the thread.

author: nctnico
author_rank: Super Contributor
timestamp: June 01, 2020, 09:18:45 am
content: Quote from: egonotto on June 01, 2020, 05:10:10 amBut you still can't see below the noise floor of the front-end and the dynamic range of the ADC. At some point you are looking at the performance of the analog front-end instead of a signal.

author: Fungus
author_rank: Super Contributor
timestamp: June 01, 2020, 02:33:34 pm
content: Quote from: tautech on June 01, 2020, 09:10:04 amIs that "below $300"?

author: khutch004
author_rank: Contributor
timestamp: June 01, 2020, 04:21:13 pm
content: Quote from: Fungus on June 01, 2020, 02:33:34 pmNo, it's $379 and less than $360 with a well known discount. The question is, which is more important to you, $60 or good FFT performance? Your answer may legitimately be different than mine but when I considered everything I went with the $499 (before discount) member of that family and FFT performance was one of the big factors in choosing that series.

author: Wolfgang
author_rank: Super Contributor
timestamp: June 01, 2020, 05:26:58 pm
content: Quote from: Elasia on June 01, 2020, 01:16:34 am... even a simple Python script can do that if no MATLAB is available

author: Fungus
author_rank: Super Contributor
timestamp: June 02, 2020, 05:36:09 am
content: Quote from: khutch004 on June 01, 2020, 04:21:13 pmFeel free to upload evidence to the contrary but I'm not convinced that Siglents have good FFT performance. See this thread from the other day:https://www.eevblog.com/forum/testgear/fnirsi-1013d-100mhz-tablet-oscilloscope/msg3084923/#msg3084923"Better than a Rigol DS1054Z" isn't much of a yardstick when looking at FFTs.The GW-Instek is similarly priced to your Siglent but does a much better job. The Micsigs are also better,

author: TK
author_rank: Super Contributor
timestamp: June 02, 2020, 05:59:39 am
content: Quote from: Fungus on June 02, 2020, 05:36:09 amThe GW-Instek GDS1054B is priced at $310 at tequipment

author: Fungus
author_rank: Super Contributor
timestamp: June 02, 2020, 07:33:20 am
content: Quote from: TK on June 02, 2020, 05:59:39 amAnybody on the market for an entry level scope should be grabbing one, it's a complete bargain at that price!

author: jjoonathan
author_rank: Frequent Contributor
timestamp: June 02, 2020, 02:17:03 pm
content: Ooh, good catch! The GW Instek is in a completely different FFT league from the rigol and siglent.

author: tautech
author_rank: Super Contributor
timestamp: June 02, 2020, 02:36:44 pm
content: Quote from: jjoonathan on June 02, 2020, 02:17:03 pmYep, Dave hated it.Really, Fungus links a 4 year old video on FFT shootout and thinks it's relevant to todays offerings ?

author: nctnico
author_rank: Super Contributor
timestamp: June 02, 2020, 02:43:09 pm
content: Quote from: tautech on June 02, 2020, 02:36:44 pmCorrect. Meanwhile GW Instek has added a spectrum analysis mode as well. But even the normal FFT mode works just fine; it is just that Dave doesn't like GW Instek for some reason. In reality the GW Instek and Siglent in the same price class are on par which isn't a surprise because the basic components are the same.

author: TK
author_rank: Super Contributor
timestamp: June 02, 2020, 03:01:52 pm
content: Quote from: tautech on June 02, 2020, 02:36:44 pmIt has not changed a lot in 4 years, has it?

author: TK
author_rank: Super Contributor
timestamp: June 02, 2020, 03:03:31 pm
content: There is another video from Dave where he tests a Near Field Probe and if I remember correctly, he gets a very nice match from a GW Instek FFT, compared to the Rigol Spectrum Analyzer that he uses as the model.

author: Gandalf_Sr
author_rank: Super Contributor
timestamp: June 02, 2020, 03:11:56 pm
content: Does the GDS1054B have serial decode and triggering?

author: Fungus
author_rank: Super Contributor
timestamp: June 02, 2020, 03:18:21 pm
content: Quote from: Gandalf_Sr on June 02, 2020, 03:11:56 pmIt does if you copy the relevant firmware modules onto the internal storage.It's a modular firmware system and you can copy modules from higher-up Instek models onto lower-down models.https://www.eevblog.com/forum/testgear/possible-gw-instek-gds-1000b-hack/They also have 4 channels (with per-channel controls) and a proper push button next to the twisty knob - no more pushing twisty knobs to select things.

author: Fungus
author_rank: Super Contributor
timestamp: June 02, 2020, 03:22:13 pm
content: Quote from: tautech on June 02, 2020, 02:36:44 pmWhat's changed since that video?(...apart from the Rigol DS1054Z getting a firmware update to do FFT from memory instead of "screen")

author: TK
author_rank: Super Contributor
timestamp: June 02, 2020, 03:25:35 pm
content: Quote from: Fungus on June 02, 2020, 03:18:21 pmIt is now included standard (official) with the latest firmware update

author: TK
author_rank: Super Contributor
timestamp: June 02, 2020, 03:29:35 pm
content: Quote from: Fungus on June 02, 2020, 03:18:21 pmI am waiting for my unit to arrive to test if the hack still works with the latest firmware. I had one in the past and I was able to downgrade to a firmware that supported the hack, then you can upgrade from there. In theory you can hack to 200MHz and I remember measuring signals all the way up to 300MHz or above

author: khutch004
author_rank: Contributor
timestamp: June 02, 2020, 06:23:13 pm
content: Quote from: Fungus link=topic=243619.msg3086244#msg3086244 date=1591076169The GW-Instek is similarly priced to your Siglent but does a much better job.[/quote

author: jjoonathan
author_rank: Frequent Contributor
timestamp: June 02, 2020, 07:14:02 pm
content: Quote from: tautech on June 02, 2020, 02:36:44 pmAre siglent's current entry-level scope FFTs still this bad:https://youtu.be/Cwbwq-AKbPc?t=475?

author: 2N3055
author_rank: Super Contributor
timestamp: June 02, 2020, 07:42:26 pm
content: Quote from: jjoonathan on June 02, 2020, 07:14:02 pmNo.

author: Fungus
author_rank: Super Contributor
timestamp: June 02, 2020, 07:48:16 pm
content: Quote from: khutch004 on June 02, 2020, 06:23:13 pmWhat if it's only $310?https://www.tequipment.net/Instek/GDS-1054B/Digital-Oscilloscopes/?search=true

author: nctnico
author_rank: Super Contributor
timestamp: June 02, 2020, 08:18:02 pm
content: And don't forget the Tequipment EEVblog discount. Don't know how much it is exactly but 5% already takes the GDS-1054B below $300.

author: TK
author_rank: Super Contributor
timestamp: June 02, 2020, 08:38:51 pm
content: Quote from: nctnico on June 02, 2020, 08:18:02 pmDon’t tell me they also have EEVblog discount! Well, little bit late for me but good news anyway

author: rsjsouza
author_rank: Super Contributor
timestamp: June 02, 2020, 08:50:31 pm
content: Quote from: tautech on June 02, 2020, 02:36:44 pmThe FFT on the Instek looks alright, but the interface is terrible with having to go back and forth on the buttons to change the center, span and magnitude. I can see why he hated it; I would as well.

author: nctnico
author_rank: Super Contributor
timestamp: June 02, 2020, 08:53:07 pm
content: Once you get the hang of it, it is actually is quite productive for doing real measurements. I've used my GW Instek scope's FFT function extensively during the development of a project a couple of years ago.

author: gfmucci
author_rank: Regular Contributor
timestamp: June 07, 2020, 01:02:30 am
content: Quote from: nctnico on May 31, 2020, 08:46:55 pmI don't have an extra computer to devote to the bench and not another $1K for one, so no Discovery 2.And yes, use is for audio frequency, distortion testing and diagnostics. The newish Rigol DS 1202Z ($299; ~$30 less than current Intek previously mentioned) has 24M bit depth which I thought would help with fft.

author: TK
author_rank: Super Contributor
timestamp: June 07, 2020, 02:00:48 am
content: FFT on Rigol is bad. The GDS1054B is less than $300 if you apply the eevblog coupon. The 24Mpts does not help with FFT

author: Fungus
author_rank: Super Contributor
timestamp: June 07, 2020, 04:02:52 am
content: Quote from: gfmucci on June 07, 2020, 01:02:30 amThe FFT on that series of Rigols is awful, limited to 64k points and terrible UI. Donotbuy one if "use is for audio frequency, distortion testing and diagnostics".(if that really is the main use for this then get an Analog Discovery instead, it has 14-bit ADC for much lower noise floor and built-in signal generator for bode plots)

author: TK
author_rank: Super Contributor
timestamp: June 07, 2020, 07:22:54 am
content: DS1000Z vs GDS-1054Z FFT comparison video

author: Gandalf_Sr
author_rank: Super Contributor
timestamp: June 07, 2020, 10:29:44 am
content: Yes the GW Instek GDS-1054Z has a 'better' FFT than the Rigol DS1054Z but the UI on the GDS-1054Z is "Ugh" according Dave Jones' video comparing many O'scope brands.It's like asking which is the better 50" TV to buy when I have only $50 to spend.My point being that, if you really want to do FFT, you'd be better bumping up your budget to the $600 - $900 range.If you really want to do spectrum analysis, buy a spectrum analyzer.

author: nctnico
author_rank: Super Contributor
timestamp: June 07, 2020, 10:38:07 am
content: Quote from: Gandalf_Sr on June 07, 2020, 10:29:44 amThe UI on the GW Instek isn't that bad. It is just compact with dual function keys in order to minimize the number of menus to go through. And nowadays GW Instek has a spectrum analysis mode as well.

author: Fungus
author_rank: Super Contributor
timestamp: June 07, 2020, 11:07:27 am
content: Quote from: Gandalf_Sr on June 07, 2020, 10:29:44 amHe also said, "...ultimately, itcando the business".

author: Gandalf_Sr
author_rank: Super Contributor
timestamp: June 07, 2020, 12:22:53 pm
content: I'm not bashing GW Instek and I'm certainly not saying that the DS1054Z has a usable FFT; I watched the video and I see why Dave described the UI controls for the FFT function on the GDS-1054Z as "Ugh". This has fired me up to go into my mancave and test out the FFT FUNctionality of my Rigol MSO5074. I repeated Dave's FFT test on my MSO5074 and it works like a dream...

author: Fungus
author_rank: Super Contributor
timestamp: June 07, 2020, 02:01:33 pm
content: Quote from: Gandalf_Sr on June 07, 2020, 12:22:53 pmNot exactly "below $300" though.If we're going to be strict about the competition rules then here's a signal with four harmonics being shown on my DSO Quad:It updates at full screen rate. It also has a built-in signal generator and can do Bode plots. They cost about $160.nb. The signal is coming from a digital pin on an Arduino going into an RC filter so S:N ratio is about 48dB.

author: Gandalf_Sr
author_rank: Super Contributor
timestamp: June 07, 2020, 02:31:02 pm
content: What's a DSO Quad? The graphics look like an old Pong machine.

author: Fungus
author_rank: Super Contributor
timestamp: June 07, 2020, 02:51:26 pm
content: Quote from: Gandalf_Sr on June 07, 2020, 02:31:02 pmhttps://www.ebay.com/sch/i.html?_nkw=dso+quad

author: gfmucci
author_rank: Regular Contributor
timestamp: June 07, 2020, 03:34:15 pm
content: Quote from: Gandalf_Sr on June 07, 2020, 10:29:44 amWhen I receive your $500 check in the mail, I'll consider your recommendation. Even then I might use the $500 to pay next month's mortgage.As for 55" tv's, I got a perfectly fine one for $350 a few months ago. And yes, if I wanted to be a tv elitist, I know I could spend over a few grand. I find that some have the same view of scopes.Consider me in the Fungus camp, or even a few levels below. I have seen videos by audio techs using their scope to measure >0.1% amplifier harmonic distortion using scopes rated fairly poorly for their fft function.https://youtu.be/n8hNrDcJMCwI was looking for something that is considered the top of the heap with regard to fft, maybe a little or somewhat better than what the audio guy was using for under $300. It looks like the GW Instek fits the bill, with the only downside being a little more knob fiddling being required.Thanks for the recommendations. The GW will be added to my "maybe" list.

author: Mr. Scram
author_rank: Super Contributor
timestamp: June 07, 2020, 03:39:43 pm
content: I've seen a DS1054Z used to pipe data to a PC for FFT a long time ago and I've been surprised this isn't much more common. I see some people talking about Matlab or Python here but there doesn't seem to be any common program or method, despite proper spectrum analyzers still being stupidly expensive. Is anyone willing to share their method or setup?

author: nctnico
author_rank: Super Contributor
timestamp: June 07, 2020, 04:20:07 pm
content: IIRC Mechatrommer has written an FFT application for the DS1054Z but the update rate will be very low. The advantage of having FFT on an oscilloscope is that it is -somewhat- realtime with updates less than 1 second apart.

author: Fungus
author_rank: Super Contributor
timestamp: June 07, 2020, 04:47:37 pm
content: Quote from: gfmucci on June 07, 2020, 03:34:15 pmI don't know how long that offer will stand but $300 isnota normal price for the Instek.Normally they cost a lot more than that.

author: Gandalf_Sr
author_rank: Super Contributor
timestamp: June 07, 2020, 04:48:17 pm
content: Knob twiddling is overrated. Rigol DS1054Z FFT sucks but other than that, it's a great scope.I struggled with the price point on the TV example, CostCo are selling a 55" 4k TV for $280shame they don't sell oscilloscopes

author: Antonio90
author_rank: Frequent Contributor
timestamp: June 07, 2020, 04:50:21 pm
content: Quote from: gfmucci on June 07, 2020, 01:02:30 amI'm not really in a position to recommend anything, but if you are considering the Analog Discovery, you can probably get a second hand laptop in ebay for ~30-50 bucks working perfectly. My lab computer is a Thinkpad x220 I found for 40€, and second hand computers are usually much more expensive in Europe than in UE. Right now my mother, one of my brothers an a friend of mine are using laptops from 40-60€, it's been a bit more than a year and not a single hardware problem.

author: Mr. Scram
author_rank: Super Contributor
timestamp: June 07, 2020, 06:00:29 pm
content: Quote from: nctnico on June 07, 2020, 04:20:07 pmI've seen a reasonable performing PoC a long time ago. This convinced me a lot should be possible when properly optimized. Unfortunately that software is long gone.https://hackaday.com/2015/09/22/a-better-spectrum-analyzer-for-your-rigol-scope/

author: Wolfgang
author_rank: Super Contributor
timestamp: June 07, 2020, 06:10:35 pm
content: Quote from: Mr. Scram on June 07, 2020, 06:00:29 pmThe software is still there, but you need to port it to Python3. It will not do wonders, but as a monitor its not too bad. For a usable FFT you need a high-res scope, otherwise the dynamic range is simply not good enough even for trivial tasks.