Siglent SDS5034X scope: Voltgaes allowed to apply to it? - Page 1
Forum section: electronics / testgear

author: Faringdon
author_rank: Super Contributor
timestamp: January 07, 2023, 08:01:30 am
content: Hi,We want to use a bit of coaxial cable as a DIY probe to scope a leakage inductance spike which goes up to ~250Vpk.Can we put the coax into this scope directly (with a BNC connector on it)?AYK, the coax piece doesnt have the 10MEG resistor in it, its just a piece of plain coaxPeople usually say +/-300V to a scope...but this is with the 10MEG probe resistor in there?Manual and service manual doesnt sayhttps://siglentna.com/product/sds5034x-350-mhz-4-ch/

author: tautech
author_rank: Super Contributor
timestamp: January 07, 2023, 08:33:07 am
content: Quote from: Faringdon on January 07, 2023, 08:01:30 amP9 of the datasheet does under Max. Input voltagehttps://int.siglent.com/u_file/document/SDS5000X_Datasheet_EN02B.pdf

author: Performa01
author_rank: Super Contributor
timestamp: January 07, 2023, 08:57:28 am
content: The specifications clearly state max. input voltage @ 1 MΩ ≤ 400 Vpk(DC + AC), (DC~10 kHz).So the real question is about the frequency spectrum of that signal. If the rise time of that spike is not faster than 35 µs, you should be totally safe. But even if it is faster, it is unlikely that the input circuitry will suffer damage from a moderate overload lasting only a few microseconds.The 10 kHz apply to a continuous sine wave and not a spike with low repetition rate.It all comes down to the total energy pumped into the scope input. This in turn quite obviously depends also on the physical size of the inductor...

author: 2N3055
author_rank: Super Contributor
timestamp: January 07, 2023, 09:56:55 am
content: Scope is grounded instrument.What are you measuring and how?Please explain exactly.If you never measured it, how do you know what spike voltage is?Safe way of measuring high voltage/ high energy is having safety reserve..If DUT is floating and can be safely connected to scope then you could use normal passive 100x probe rated for 1000-1500V. There are dozens of them to buy, some very inexpensive.If DUT is part of something grounded, then you need high voltage differential probe.SDS5000X is not cheap scope. Damaging it because you try to save money on probing is not cheaper long term...

author: Faringdon
author_rank: Super Contributor
timestamp: January 08, 2023, 08:15:06 am
content: QuoteThanks, this scope must not be menat for use with SMPS, as only giving the voltage rating for up to 10khz, is totally no good for SMPS work....just thinking of eg flyback drain voltages etc etc etc....Also, i assume they mean its 400vpk when you use a 1:1 probe?Presumably if you use a 10:1 probe then its 4000Vpk?I just connected this scope via a 10:1 probe to a node which was pulsing up to 200V for some 100ns every 3.3us.....i hope ive not damaged it?

author: tautech
author_rank: Super Contributor
timestamp: January 08, 2023, 09:10:26 am
content: Quote from: Faringdon on January 08, 2023, 08:15:06 amOr BNC connection.QuoteOnly if the probe is rated for such which is very unlikely for a 10x probe let alone a 100x probe but 1000x probes are in these voltage ratings.QuoteSDS5000X models all come with fixed 10x self sensing SP3050A probes rated to 400V RMS CAT II.https://siglentna.com/wp-content/uploads/dlm_uploads/2022/08/Probe_DataSheet-E01B.pdf

author: rf-loop
author_rank: Super Contributor
timestamp: January 08, 2023, 10:25:36 am
content: Quote from: Faringdon on January 08, 2023, 08:15:06 amPresumably if you use a 10:1 probe then its 4000Vpk?Why you do these things and have oscilloscope if you write this sentence.Have you ever looked any probe specifications.Btw, also after DC there is also voltage derate curve vs frequency.Some examples about other oscilloscopes.Do you think no one is good or not meant for work with SMPS circuits.Also one question. Why connect with just plain coaxial to oscilloscope 1M input. Also I may ask: what is coaxial length and how its capasitance affect DUT.Please explain real reasons. Or is it just for playing fun without enough experience and knowledge until smoke come come out (do you know all electrics and electronics works using smoke and when it leaks out then it do not work anymore).Tektronix MSO54BMaximum input voltage1 MΩ: 300 VRMS, CAT IIderateat 20 dB/decade from 4.5 MHz to 45 MHz;at 14 dB/decade from 45 MHz to 450 MHz; > 450 MHz, 5.5 VRMSR&S®RTM3004at 1 MΩ 300 V (RMS), 400 V (Vp),derates at 20 dB/decade to 5 V (RMS) above 250 kHzTeledyne LeCroy HDO4000AMaximum Input Voltage 50 Ω: 5 Vrms, 1 MΩ: 400 V max (DC + Peak AC ≤ 10 KHz)Teledyne LeCroy Waverunner 9000Maximum Input Voltage 50 Ω: 5 Vrms ±10 V peak; 1 MΩ: 400 V max. (DC + peak AC < 10 kHz)Rigol DHO40001 MΩ CAT I 300 Vrms, 400 Vpk (DC + Vpeak)Take example this Rigol and connect its input to example 200MHz 200Vrms. Is it ok because well inside data sheet (except there read CAT I. Think if it cover also high frequencies)Many many oscilloscopes do not have any specs about input max V derating vs frequency. Nothing about frequency and sure there still is limits - are there any oscilloscope user who really do not understand this. Oscilloscopes are made for educated engineers who need understand least simplest basics.One EEVblog thread for you to read...https://www.eevblog.com/forum/testgear/rigol-ds1202z-e-input-voltage-vs-frequency-derating/Also noted you talk about short peaks, not continuous wave.But yes, it is sad oscilloscopes inputs are not better specified and a good defense is not that others do the same.Normally in this kind of test we use probes, not direct coaxial and even more weightednotwithout any impedance matching.

author: rf-loop
author_rank: Super Contributor
timestamp: January 08, 2023, 10:30:05 am
content: Quote from: tautech on January 08, 2023, 09:10:26 amAs you can see there is one very sad thing. It is named as probe DataSheet. And "data sheet" do not include even voltage derate curves vs frequency.This is not real data sheet at all in my rating scale. It is more like poor sales catalog - brochure.

author: tautech
author_rank: Super Contributor
timestamp: January 08, 2023, 05:33:33 pm
content: Quote from: rf-loop on January 08, 2023, 10:30:05 amYes of course but sometimes an overview is sufficient however the probe datasheets are not hard to find except on the HQ and EU site that really needs some improvements.From the NA site finding SP3050A probe datasheet is not hard:https://siglentna.com/wp-content/uploads/dlm_uploads/2022/08/SP3150ASP3050A-1.pdf

author: rf-loop
author_rank: Super Contributor
timestamp: January 08, 2023, 07:30:41 pm
content: Quote from: tautech on January 08, 2023, 05:33:33 pmYes,it isInstructions Guide what can also read as data sheet!

author: Martin72
author_rank: Super Contributor
timestamp: January 08, 2023, 09:40:13 pm
content: Quote from: Faringdon on January 08, 2023, 08:15:06 amNever.Even a 100:1 probe didn´t reach that value:https://www.batronix.com/shop/measurement/probes/Testec-TT-HV-150.htmlReasons are isolation, max voltage across one resistor, lack of airgaps...We always use a differential probe when measuring on smps, especially on primary switched ones.And/or when measuring on more than one channel - because of the grounding.Scope is grounded and every of it´s inputchannel too(normally).If you want to measure on primary and secondary side at the same time and use normal probes, nevertheless if 10:1 or 100:1 or 1000:1, you short the secondary output to ground then - Not good...