Fnirsi DPOS350P - Page 1
Forum section: electronics / testgear

author: fjriii
author_rank: Newbie
timestamp: May 01, 2025, 09:32:59 pm
content: First and foremost, I am new here and wanted to say hi. I recently found these forums when looking for info on the Fnirsi DPOS350P. I have come to realize that I may be one of the first people to receive one of these, so I wanted to share some pictures and feedback. I am an IT professional, hobbyist luthier, and the occasional builder of amps, pedals, and other miscellaneous electronics projects. I graduated 20+ years ago from college with a bachelors in computer technologies, which consisted of a 50/50 split between computer science and electrical engineering. I never really used the EE aspect of my degree, with the exception of misc personal projects, so I am very rusty compared to others here in these forums. I bought this scope as I needed something on my bench to assist with my latest guitar amp build. Just sharing this so I dont get skewered by some of the opinions of others that I have seen on other fairs products. I am happy to share more about the device to anyone looking to know more.Initial impressions:the side LED lights are pointless, but don't see an option to disable them.the fan is a little noisy, nothing obnoxious, but its always running and whines some if laid flatthe case was unexpected, as it wasn't mentioned on their websitethe probes color rings they included don't match the colors used on screen, a very odd decision...the UI has been easy enough too figure out, even for somebody that hasn't used a scope in 20 years

author: Xena E
author_rank: Frequent Contributor
timestamp: May 01, 2025, 10:50:55 pm
content: Hello and welcome.One of the things that is most useful to know about a newly introduced scope is its ability to resolve narrow pulses.Though personally I feel they do makesomereasonable quality products, Fnirsi do sometimes like manipulating their headline specifications, so I wonder if you've tested it WRT its claimed sampling rate?Often the manipulation of actual specifications mean that claimed bandwiths are of the "can just meet specs with sinewave input, one channel driven" type!I haven't studied this device, my usual minimum bench mark is a sample per second rate 25× higher than bandwidth to be pleasingly useful, often cheap scopes (generally), are claimed as little as 5× and often don't even meet that!Just Wonder what your observations on that are with this new scope? ... although with your suggested use case (audio), I'm sure that this is not going be a problem with it.Regards,X

author: BillyO
author_rank: Super Contributor
timestamp: May 01, 2025, 11:31:38 pm
content: Quote from: Xena E on May 01, 2025, 10:50:55 pmAbsolutely hilariousSo the 6GHz Keysight DSOX6004A is a "cheap scope" at only $62K and couldn't possibly meet your demanding needs because the sample rate is only 3.33 times the BW!Name one 350 MHz scope that has a sample rate of 8.75GHz!

author: Xena E
author_rank: Frequent Contributor
timestamp: May 01, 2025, 11:54:39 pm
content: Quote from: BillyO on May 01, 2025, 11:31:38 pmKinda fucked that post up huh?Put your own figures and decimals places in where you want themits been a tiring day.Regards,X

author: coromonadalix
author_rank: Super Contributor
timestamp: May 02, 2025, 12:08:47 am
content: we paid around 33k $ Cad for an 4Ghz bw at 20 giga sampling sds7404a loll cheap price loll

author: wolfy007
author_rank: Frequent Contributor
timestamp: May 02, 2025, 05:47:32 am
content: Yup just got mine also, lets see if they still lie about specs I suppose. Tho same initial impressions after opening up the box, that side lighting is so unnecessary.

author: Atlan
author_rank: Frequent Contributor
timestamp: May 02, 2025, 05:53:01 am
content: 3 topics started about 350......

author: ptluis
author_rank: Frequent Contributor
timestamp: May 02, 2025, 10:36:51 am
content: Quote from: Atlan on May 02, 2025, 05:53:01 amI would like to see more detailed review about those who already got the scope not just talking about side lights, that's kind of useless. 3 people already post they got the device but that's it, seems some kind of marketing...

author: Atlan
author_rank: Frequent Contributor
timestamp: May 02, 2025, 11:42:53 am
content: Maybe no one has bought it yetfake sales figures? Anyway, most reviews will be, it shows. But we won't know soon if it shows badly. We'll have to wait.

author: bte
author_rank: Regular Contributor
timestamp: May 02, 2025, 07:28:49 pm
content: Quote from: BillyO on May 01, 2025, 11:31:38 pmRigol MSO5354 comes close at 8GSa/s.

author: fjriii
author_rank: Newbie
timestamp: May 03, 2025, 01:03:12 am
content: Quote from: ptluis on May 02, 2025, 10:36:51 amSorry to disappoint, but I have nothing to do with the company. I wanted a cheap scope and this for the bill for me.

author: coromonadalix
author_rank: Super Contributor
timestamp: May 03, 2025, 01:46:50 am
content: some Fnirsi models have a github and some open source FW or reversed one ...

author: pcprogrammer
author_rank: Super Contributor
timestamp: May 03, 2025, 06:01:20 am
content: Quote from: coromonadalix on May 03, 2025, 01:46:50 amThis one is to new to have that already.@fjriii, I hope it works for you in the way that you want, but the specs on the FFT state 200kHz to 350MHz, so not much use in the audio world. Based on your original post, my guess is that you won't be able to do some proper bandwidth testing on it. (Neither can I, as my signal sources are only up to 100MHz)The useless LED lighting on the sides brings back the toy vibes though, just like the other FNIRSI scopes have.But at least the picture of the screen shows some better graphics software being used.@wolfy007, how is your setup. Can you do some proper in depth tests on this thing?Hopefully Dave gets one in the mailbag to play with. I certainly have some suggestions onto what he could look into.

author: RAPo
author_rank: Super Contributor
timestamp: May 03, 2025, 08:10:29 am
content: Does it have the advertised B(R)ANWIDTH?

author: wolfy007
author_rank: Frequent Contributor
timestamp: May 04, 2025, 12:51:45 am
content: Quote from: pcprogrammer on May 03, 2025, 06:01:20 amIll endeavor to do some basic testing today if I get the time, let me know if you want try anything. I did quickly hook it up to a Siglent siggen to compare to a Siglent SDS824X (hacked of course), took a couple quick shots with 120MHz sine and 25Mhz square for what its worth.PS: Both scopes set to 12bits, source was set to 120mV p-p, Siglent is a 200MHz BW scope, Fnirsi claimed 350MHz, the Siglent did attenuate more than the Fnirsi at this 120MHz. Only took a couple quick photos at this small signal level, no real testing done yet.

author: csuhi17
author_rank: Frequent Contributor
timestamp: May 04, 2025, 06:12:45 am
content: Quote from: wolfy007 on May 04, 2025, 12:51:45 amCan you make a single shot in the fastest time base?Fnirsi seems to be software-enhancing the signal, masking reality.Fnirsi's 12 bits are not the same as Siglent's or any other normal scope manufacturer's 12 bits.That's some kind of software magic.Maybe it's averaging, smoothing out the signal so it's not fuzzy.I think if you leave it at 8 bits the signal will be closer to reality.

author: pcprogrammer
author_rank: Super Contributor
timestamp: May 04, 2025, 06:43:48 am
content: The square wave signal already tells the story that in 12 bits mode it won't reach it's full bandwidth. The Siglent shows a flatter top and bottom due to less loss of the high frequency parts in the signal.Like csuhi17 wrote try the same signal with the scope set to 8 bits, which is it's actual ADC data width.For the 25MHz square wave the sine components are 25MHz, 75MHz, 125MHz, 175MHz, 225MHz, 275MHz, 325MHz, 375MHz, ..... with diminishing amplitude. Your Siglent with a 200MHz bandwidth, should show at least the first four without to much attenuation, the FNIRSI in 8 bit mode should show about seven. So the square should be a bit squarer on the FNIRSI.I do wonder if they again put in the code to just calculate a sine wave above some fixed frequency. A repetitive narrow pulse test might show this.Another test, requires opening the scope and measure on the four ADC's to check if they get the exact same signal when using one channel at 1GSa/s. Also checking the ADC clocks can tell if it is any good, but not sure you will be able to detect small phase differences with your Siglent scope.

author: wolfy007
author_rank: Frequent Contributor
timestamp: May 04, 2025, 10:02:42 am
content: When looking at the signal on the Siglent it is rock solid, but on the Fnirsi it has a slight jiggle, wouldnt surprise me if there is some software thing happening in the background. I did try setting between 8bit to 16bit, but I honestly couldnt tell much of a difference, granted I spent a whole 20min just checking if it would work so Im not going to just jump to conclusions.I must admit Im a sucker for this form factor tho, liked the 1013D (even tho they lied, eh its a 30MHz scope), tho I do think this one might actually be doing 1GS/s but if it is I might not be the best interleaved sampling?

author: wolfy007
author_rank: Frequent Contributor
timestamp: May 04, 2025, 10:26:46 am
content: Couldnt help myself, quick play before bed;

author: wolfy007
author_rank: Frequent Contributor
timestamp: May 04, 2025, 10:28:03 am
content: and 400MHzPS:5ns/div is the shortest timebase setting, so I set both scopes to 5ns/div

author: csuhi17
author_rank: Frequent Contributor
timestamp: May 04, 2025, 10:31:05 am
content: Quote from: wolfy007 on May 04, 2025, 10:02:42 amMaybe it know 1GS/s, but it is questionable at what cost?Quote from: pcprogrammer on May 03, 2025, 06:13:53 amAs pcprogrammer wrote: " A repetitive narrow pulse test might show this."Single trigger and rare narrow pulse in the fastest, smallest time base.

author: pcprogrammer
author_rank: Super Contributor
timestamp: May 04, 2025, 10:46:12 am
content: Quote from: wolfy007 on May 04, 2025, 10:02:42 amThat is also why I bought the 1013D back then. I wanted something small for use on the computer bench. Have not used it once for actual work so to speak.Quote from: wolfy007 on May 04, 2025, 10:26:46 amThat sine wave on the DPOS350P looks way to smooth to be real.Your other scope should be up to the task of testing the phase differences in the ADC input signals and the sampling clocks of the DPOS350P though.

author: wolfy007
author_rank: Frequent Contributor
timestamp: May 04, 2025, 11:01:02 am
content: Ill try the Pulse test some time during the week, as for sampling the internals that will have to wait for next weekend I think.And yes the sample capacity is definitely a mistake.

author: wolfy007
author_rank: Frequent Contributor
timestamp: May 04, 2025, 12:15:24 pm
content: HMMMM, one more quick test with a Leo Bodnar fast rise gen on DSO9064A, SDS824X HD and the Fnirsi;

author: csuhi17
author_rank: Frequent Contributor
timestamp: May 04, 2025, 05:53:08 pm
content: Quote from: wolfy007 on May 04, 2025, 12:15:24 pmDid you catch the signal with a single shot trigger, or was it triggered in AUTO mode and did you manually press the stop button?

author: wolfy007
author_rank: Frequent Contributor
timestamp: May 04, 2025, 10:51:35 pm
content: Yeah was in AUTO and I manually pressed Stop, then moved the Bodnar siggen to the next scope.

author: BillyO
author_rank: Super Contributor
timestamp: May 10, 2025, 03:12:54 am
content: Quote from: wolfy007 on May 04, 2025, 10:51:35 pmWas 50Ω termination used in all cases?

author: Serhii74
author_rank: Contributor
timestamp: October 07, 2025, 07:29:32 pm
content: It's very accurate, starting at 0.1 Hz in DC mode and 3 Hz in AC mode.It's definitely suitable for audio equipment.

author: Jan Steinman
author_rank: Contributor
timestamp: October 08, 2025, 01:41:38 am
content: Quote from: bte on May 02, 2025, 07:28:49 pmThat's a scope that costs ten times as much as the FNIRSI DPOS350P.The Tek scopes I'm most familiar with sampled at four times the front-end 3db bandwidth.