Is it possible to use oscilloscope in this case? - Page 1
Forum section: electronics / beginners

author: Bondguy
author_rank: Contributor
timestamp: November 02, 2016, 06:22:45 pm
content: Is it possible to check the voltage (of about 220V ) between cathode and anode of a thyristor with oscilloscope? I would use an isolation transformer but what else must I be aware of?

author: WackyGerman
author_rank: Regular Contributor
timestamp: November 02, 2016, 06:32:45 pm
content: You better use a multimeter for that . It s more accurate and much easier

author: Bondguy
author_rank: Contributor
timestamp: November 02, 2016, 07:26:23 pm
content: Oscilloscope is more useful because you can see all details (e.g. oscillating )

author: WackyGerman
author_rank: Regular Contributor
timestamp: November 02, 2016, 07:36:33 pm
content: Yes that s right . If you want to see the details it is more handy but you need additional equipment for safe measurements i.e. differential probe . In this case it would be the easiest way to use a scopemeter with floating inputs . You don t need to care about the earth potential in this case . But a scopemeter is not that cheap unfortunately

author: Bondguy
author_rank: Contributor
timestamp: November 02, 2016, 08:25:50 pm
content: But if I use an issolation transformer I do not need to care about the earth potential either. Or am I wrong?

author: WackyGerman
author_rank: Regular Contributor
timestamp: November 02, 2016, 08:43:25 pm
content: Well if you do that then you have the problem that your oscilloscope will blow up because the voltage is too high . You say you have 220 Volt at the thyristor . That s the RMS value . So be careful , the inputs of your scope may be marked with 400 V or 200 V Peak max and that s the peak value .So that s U PP max =400 V . Just calculate . U RMS x 1,4 = U Peak , 220 x 1,4 =308 V Peak , U PP = U Peak x 2 . So you would feed 616 V PP into your oscilloscope

author: Bondguy
author_rank: Contributor
timestamp: November 02, 2016, 08:56:16 pm
content: What is RMS value?Can you explain?Can you explain a little more the calculationJust calculate . U RMS x 1,4 = U Peak , 220 x 1,4 =308 V Peak , U PP = U Peak x 2 . So you would feed 616 V PP into your oscilloscopeThanks

author: danadak
author_rank: Super Contributor
timestamp: November 02, 2016, 09:40:12 pm
content: If its a 2 channel scope then use it differentially, use the "Add" function, and the "invert"selection on channel 2.https://www.eevblog.com/forum/beginners/how-to-perform-differential-voltage-measurement-with-an-oscilloscope/http://users.rowan.edu/~mease/resources/Fundamentals%20of%20Floating%20Measurements%20and%20Isolated%20Input%20Oscilloscopes.pdfRegards, Dana.

author: alsetalokin4017
author_rank: Super Contributor
timestamp: November 02, 2016, 11:13:04 pm
content: What if my scope's inputs are marked 300V RMS? (For example DS1054z)What if I use one, or a pair, of 10x attenuating probes?What if I use one, or a pair, of 100x attenuating probes?

author: janoc
author_rank: Super Contributor
timestamp: November 03, 2016, 12:09:01 am
content: Quote from: alsetalokin4017 on November 02, 2016, 11:13:04 pmYou should use a high voltage and, ideally, differential probe. Normal probes (even the 100x ones) arenotdesigned to handle such voltages. E.g. the stock probes that come with DS1054Z are labeled 1x 100V or 10x 300V max. You finger slips, you move the switch on the probe while it is live and KABOOM.

author: danadak
author_rank: Super Contributor
timestamp: November 03, 2016, 02:01:00 am
content: Some specs -http://datasheet.octopart.com/RP2200-Rigol-datasheet-26580153.pdfhttps://en.wikipedia.org/wiki/Measurement_categoryhttps://forum.tek.com/viewtopic.php?f=568&t=136026http://support.fluke.com/find-sales/download/asset/1263690_6116_eng_h_w.pdfRegards, Dana.

author: vk6zgo
author_rank: Super Contributor
timestamp: November 03, 2016, 09:28:50 am
content: Quote from: WackyGerman on November 02, 2016, 08:43:25 pmIn an ac waveform,peak to peak voltages aren't real-----the positive & negative half cycles aren't present at the same time!Peak voltage is as much as you get,which is 1.414 times RMS for a sinewave & some other waveforms.P-p is really only to make it easy to measure voltages with an analog Oscilloscope (count the squares),or to determine the undistorted operating range of an amplifier stage,ADC,or similar.

author: kao
author_rank: Newbie
timestamp: November 05, 2016, 08:12:31 pm
content: Quote from: alsetalokin4017 on November 02, 2016, 11:13:04 pmIf the oscilloscope can measure up to 300 Vrms, 220 Vrms the measure can beHowever, you must comply with all safety precautions of manual. Usually it is an isolated power supply oscilloscope, for example, an isolation transformer or battery power, the right mode choice and divider probes.Measurement 220Vrms mains via OWON XDS3102 oscilloscope with battery (see from 15:25, only russian language, sorry):