Fnirsi 2031h as a first hobby oscilloscope - Page 1
Forum section: electronics / testgear

author: IWantABoobyOscilloscope
author_rank: Newbie
timestamp: May 20, 2021, 04:11:58 pm
content: HiI'm looking for my first hobby oscilloscope which I use for measuring noise of various smps circuits, cellphone/laptop chargers and desktop psu.I have 2 options:Fnirsi 2031h for 55$, this one is not as famous as another (fake specs) one, if the specs are real I feel it fit me well. But I can't find any review or teardown of this modelOwon HDS242 for 103$, as all the reviews I read this have the best sample rate for the price (250MSPS), but i feel it a bit overkill for me, and I have a dmm anywayWhat are your suggestions?

author: ledtester
author_rank: Super Contributor
timestamp: May 20, 2021, 04:46:56 pm
content: Some (self-reported) specs:Code:Fnirsi OwonMin. Vertical Sensitivity: 50 mV/div 10 mV/divMin. Horizontal Time Base: 250 ns/div 5 ns/divFnirsi specs:http://fnirsi.cn/productinfo/392305.htmlOwon specs:https://www.owon.com.hk/products_owon_hds200_series_digital_oscilloscopeWhether the scopes operate as expected at these settings is another question.Btw - this is a good video on how to measure noise in a switching power supply:Engineer It - How to test power supplies - Measuring Noise - Texas Instrumentshttps://youtu.be/pKXPqApOYfkNote the scope settings that are used to make the two measurements in the video...for ripple, vertical sensitivity is 10 mV/div and the 20 Mhz bandwidth limiter is enabledfor the transient, the vertical sensitivity is 100 mV/div but the time base is 5 ns/div and the bandwidth limiter is not enabled(Of course, both units are basically 20 MHz bandwidth limited by design.)

author: Fungus
author_rank: Super Contributor
timestamp: May 20, 2021, 04:50:07 pm
content: I don't know about those particular models but theonlynumber you should be looking at for"measuring noise of various smps circuits, cellphone/laptop chargers and desktop psu"is the sensitivity number (which they don't usually publish).eg. There's similar FNIRSIs that won't show anything much below about 50mV - completely useless for you.https://www.eevblog.com/forum/projects/reverse-engineering-fnirsi-5012h/msg2775670/#msg2775670https://www.eevblog.com/forum/testgear/fnirsi-1c15-handheld-scope/msg3468494/#msg3468494

author: tunk
author_rank: Super Contributor
timestamp: May 20, 2021, 05:20:59 pm
content: There's a test here, and it looks like the real bandwidth could be around 15MHz:https://translate.google.com/translate?hl=en&sl=ru&u=https://mysku.ru/blog/aliexpress/77475.html&prev=search&pto=aueThere's also the Hantek 2C42, and SigPeak DSO2512G (claimed 10mV/div, real bandwidth maybe 30MHz):https://www.eevblog.com/forum/testgear/new-2ch-pocket-dsosg-sigpeak-dso2512g/

author: IWantABoobyOscilloscope
author_rank: Newbie
timestamp: May 21, 2021, 06:53:01 am
content: Quote from: Fungus on May 20, 2021, 04:50:07 pmI think that ATX standard allow ripple up to 50 mV so I think it's ok. What do you think?Quote from: tunk on May 20, 2021, 05:20:59 pmAfter read the link you provided, I think I will go with OWON, at least they dont fake the specs. I really like the design of the sigpeak (lol I thought it was a micsig ) but worry about the sample rate

author: Fungus
author_rank: Super Contributor
timestamp: May 21, 2021, 10:23:43 am
content: Quote from: IWantABoobyOscilloscope on May 21, 2021, 06:53:01 amDo you want to know how good a PSU is or only whether it's outside the standard or not?

author: IWantABoobyOscilloscope
author_rank: Newbie
timestamp: May 21, 2021, 10:51:34 am
content: Quote from: Fungus on May 21, 2021, 10:23:43 amYes I want to know how good it is. Please correct me if I'm wrong, Vertical Sensitivity is how much you can zoom in a signal right? So half a (50mV) div is 25mV, which is quite ok with me.Or the oscilloscope just show anything below 50mV a full div?

author: tunk
author_rank: Super Contributor
timestamp: May 21, 2021, 11:04:14 am
content: Also remember that setting the probe to 10x, then 50mV/div effectively is 500mV/div.

author: Fungus
author_rank: Super Contributor
timestamp: May 21, 2021, 11:06:53 am
content: Quote from: IWantABoobyOscilloscope on May 21, 2021, 10:51:34 amYes.Quote from: IWantABoobyOscilloscope on May 21, 2021, 10:51:34 amI'd want a lot better:

author: IWantABoobyOscilloscope
author_rank: Newbie
timestamp: May 22, 2021, 03:54:46 am
content: I want to ask about the probe: 1x probe limit both the voltage and the bandwidth, right?On hantek 2c42 manual, it states that 1x scope limit bandwidth to 6mhz and voltage range from 4V,40V,400V etc..and vertical sensivity vs sample rate what is more important when measure smps noise?

author: Fungus
author_rank: Super Contributor
timestamp: May 22, 2021, 07:54:10 am
content: Quote from: IWantABoobyOscilloscope on May 22, 2021, 03:54:46 amYes.Quote from: IWantABoobyOscilloscope on May 22, 2021, 03:54:46 amSensitivity - your bandwidth is already limited by the 1x probe..

author: IWantABoobyOscilloscope
author_rank: Newbie
timestamp: May 30, 2021, 04:27:45 pm
content: Hi, I got the scope and a p6100 probe along with itWhen I tried to measure my bench power supply, I see a huge noise on the scope. I assume that because just put the probe an inches near the capacitor, the scope shows signal (~300mV Vpp) and the same signal shape appears when I connect the probeIt's strange that even barrel and tip ain't get the noise awayShould I completely remove the alligator clip from the probe, And how to do it, it looks quite tight and I'm afraid with force I will break it

author: Fungus
author_rank: Super Contributor
timestamp: May 30, 2021, 09:50:55 pm
content: Quote from: IWantABoobyOscilloscope on May 30, 2021, 04:27:45 pmWhat frequency?How are you connecting the probe?

author: IWantABoobyOscilloscope
author_rank: Newbie
timestamp: May 31, 2021, 01:18:18 am
content: Quote from: Fungus on May 30, 2021, 09:50:55 pmAt 2ms/div, the frequency is 1khzThe SMPS is set at 7V/1.5A, connect to a 10W 4.7R, which paralel with a 4700uf cap and 104 ceramic cap. I hook the probe at the cap leg

author: Fungus
author_rank: Super Contributor
timestamp: May 31, 2021, 10:00:46 am
content: Quote from: IWantABoobyOscilloscope link=topic=282760.msg3579701#msg3579701 date=162242389I hook the probe at the cap leg[/quote

author: IWantABoobyOscilloscope
author_rank: Newbie
timestamp: May 31, 2021, 10:37:39 am
content: Quote from: Fungus on May 31, 2021, 10:00:46 amI attached it to the remain capacitor leg