Some people do not understand the concept of a scope. A scope is not a multimeter. The ground lead of the probe (and the ground connection on the unit itself) is connected to the earth of the power grid in your house or lab. If you connect the ground lead of the probe to anything which has a voltage directly coming from the grid , bad things will happen. Your probe may explode and you could get hurt or worse. It is a good idea to install and use an isolation transformer to protect your gear and yourself.

I just finally got my first actual scope (largely based on your reviews and input) and it's embarrassing how excited I am about this!😄 I've only ever used them in school before and I look forward to not blowing it up

Really helpful for scope newbies. Bought a Rigol DS1102Z-E as a christmas gift to myself :D Recently I aquired two old analog Hameg scopes (HM 412-1 & HM 512-6). Interestingly, these old scopes are not connected to mains earth. The instruction manual warns you about getting shocked from the scopes casing if you connect the scopes GND to a high potential.

My Rigol DSO814 is way over my head but I’m enjoying learning. Still on step one of the Velleman Oscillator Trainer. Just understanding the probes 1x and 10x function is complex right now. Yes I understand 1x vs 10x but applying it is different. The menus and language are so new to me right now but how exciting to be learning.

Hi Eddie, thanks for this video it was great

Good advice for Saelig customers too! Isolated probes or battery-powered scopes like Micsig might be helpful in some situations!

Thank you so much.

A few points: first, many if not all modern scopes with two or more inputs can be set to differential mode: it might be a switch or menu selection with "Sum" and "Difference" or "Add" and "Subtract". In this configuration, the ground clips on the probes need not be used. This is especially useful for plain old telephone lines: the wires are long and pick up large common mode noise, so if either tip or ring are grounded horrible buzzing noise is introduced. Sometimes performance suffers, and there certainly are limits to it: you can't expect to investigate noise between a pair of 1000V circuits or circuit points especially if they are ground referenced. Floating an AC line powered scope also has similar limitations: elevate the chassis high enough and it will arc from ground of the scope to line or neutral through power supply elements or nearby circuit traces. Sometimes the limits to maximum common-mode voltage are expressed on the front panel, but should be spec'd in the manual. Second, most if not all isolation transformers bridge ground across the windings by default: thus they just don't do what most people expect. Also, Ethernet connectors are fairly well isolated: if you had problems I bet you used a less common shielded STP cable: they always sound like a great idea but are usually just a big hassle, as both ends need to be well grounded. Thanks for reminding me that although dangerous internal faults in a modern scope are highly unlikely, the chances of elevating the scope chassis through the circuit under test by human error or otherwise should be carefully considered. In general, anything outside of plain vanilla should be planned carefully, with consideration of the limitations of each device in the chain and "what if" scenarios, and verified that each piece does what you expect: assume nothing.

Thanks for this awesome vid.. Thumbs up. Quick question : what kind of isolation transformer can you suggest? I am having trouble identifying the correct class of equipment. Thx!

I hooked a scope probe to a floating chassis TV once and melted an expensive Tektronix scope probe. I learned to use the 1:1 isolation transformer that day.

Someone mentioned residual current protection. Would another way be to use an rcbo to interrupt when you do misplace the ground probe? Of course isolation transformer would be a better option to let you you continue on measuring. But a 10$ breaker would be a good protector and stop damage from occuring.

Should always isolate the DUT not the test equipment. But sometimes we do things because we have to.....

Sir. I love your videos on scopes and hope you produce more. I''ve recently watched a vidoe from the, "bald engineer," in which he was showing how to use a scope. He did something that I thought couldn't be done. He connected the probe to an AC wire to show a since wave, the ground wire wasn''t visible in the shot. Is that right. I myself am working strictly with DC and ardiunos. I even disconnect the arduino from the pc and use an undrounded wall afdapter to power it when using my scope !

I have issues with not fully understanding why if a device has a floating voltage it can not cause current to flow as there may still be a potential difference between the ground and teh floating voltage. This is also causing me problems in feeling safe about attaching my pc to serial ports on alarm/telecom equipment as they are not driven by relays or optoisolators. Could someone please explain why this floating voltage does not matter.

Yes, thank for the video, well done. You didn't mention GFCI's in Australia we call them RCD's and they trip beyond 15mA in about 10 ms. So if by chance you connected the BNC ground to to neutral on your workpiece, and your probe to hot (active) on your workpiece, there would be a differential current and the RCD/GFCI would trip,,,, wouldn't it??? presuming that you are not using an I/T on your work piece 120/240vac board.

When I was a noob, I wanted to measure the ac ripple on one of my dc power supplies, and like a dummy, I connected my clip to the neg banana plug on the power supply instead of ground, and pos to pos banana. Well I blew the breaker, and blew channel A of my cheapie Hantek. Scared the crap out of me. I though that my channel A would be gone forever but months later I was able to locate an open smd series resistor with the help of a friend. Boy was I lucky! I heard you can also use A-b by discconecting your gators and conect channe B to board ground or whaterver it is you are working on but never tried that, thats not totally safe either. Good info all around!

Good stuff to know😊

Thanks

Newbie question. on a 2 channel handheld dmm oscilloscope, how do you take 2 separate voltage measurements simultaneously while the probe grounds are not isolated by design? I can only assume you cannot? I don't see the the use in a two channel where they cannot Operate independently.

Another way is to use a non grounded scope such as a Fluke scopemeter or in my case a Micsig tablet for automotive use with all the options great scope and safe in that regard

Newby question - I think I did exactly what you are saying NOT to do in this video. In trying to get a sine wave going I attached just the ground lead of the probe to a 120V outlet (which is attached to the scope) and got a big POP! Orange flare sparks and everything. The scope seems to still be working - as in it didn't turn off. Did I damage anything internally to the oscilloscope? I'll never do that again. lol.

I have a scope that I've hardly used because I'm scared 💩less of blowing it up. I think (sometimes) the best way is running everything from an isolation transformer and use a differential probe?..... Unfortunately I haven't found any bags of money.

i run an isolation transformer on the equipment I’m testing...are you advising to run isolation on scope instead?? also...would you advise 10: 1 or 100:2 probes..I’really paranoid about o-scope safety etc...thanks

oh thank you, I'm quite cautious about that but I assumed the usb of the scope had a built-in isolator. Kinda weird to me that a scope company would not care about creating a ground loop.

as for the "pc connection": for the USB-port I'm with you - the shield is usually connected all the way thru - as for a RJ45 ether jack? at least from my personal experience most (as in more than 50%) of both the plug as well as the socket are made from plastic and only the up to 8 pins are actual connected also ethernet connections are usually galvanic isolated - so although the ethernet cable itself carries the information it's floating in respect to "machine" it's hooked into - so there won't be any galvanic connection between a scopes ethernet port and a pc one tldr: in difference to a usb connection an ether connection should not cause a ground loop as neither the 8 conductors nor the outer shield is galvanic connected all the way thru (hence shielded cables are kind of a scam as the shield is floating as its not connected to anything) but I'm open to get corrected

Well done

Great warning!! :-) If I did understand correctly, you talked about only using one earth from one probe while not using earth on the other, an that could give noise, why if all probes do use the same ground in the scope-side? Would an other solution be to connect all the ground leads together at one point?

Hey! great video! I got a question... Can I attach the ground clip (the black alligator clip) of the probe to Earth Ground and the probe to live?

This is one of the most complex and complicated issues in electronics (for me). I've read so many do's and don'ts and now I'm more confused than ever. So, how do you hookup your workbench? Do you ONLY plug the DUT (Device Under Test) to the isolation transformer? I think that's what they recommend for working on old Ham radios that don't have a power transformer - that have a "live" or "hot" chassis. Or, do you ONLY plug your test instruments into the isolation transformer and have the DUT plugged into house power? Or, do you plug everything into the isolation transformer? I think I've read that that can be dangerous, too. In any case, I guess it's a good idea to have a GFCI (Ground Fault Circuit Interrupter) (like used in bathrooms) multiple outlet bar to have the fastest shutdown of power if an imbalance in circuit power is detected. Another question I have is - do I need (would it be useful to have) one of those Siglent SDS1202's to troubleshoot a bunch of old Tektronix 465 oscilloscopes I have? I think I'm looking for an excuse to buy one. My rationale is that I don't know how functional or accurate any of those old 465's are and the Siglent would be new and better able to give me super accurate readings, wouldn't it? Maybe? Or would I be better off spending my money on other things?

Isolating the unit your are checking is the safe way..

Did something similar on my siglent 1104ex “3” channel…when testing an amplifiers 20-20k sweep I without fireworks or any signs blew channel ones input. I got no pops nor the oscope turning off. Everything is just so on the 2,3,4 channels. But the next time I turned on the scope my readings were off on channel one, i try to compensate for this ridiculous looking wave that I cannot compensate with the probe, it looks like an old picture of a 50s saucer dish UFO on its side. Ive factory restarted and put it back to factory but I realized I must have shorted out my input on channel one. I have the 1104ex and its my first real digital scope so I still have 3 channels that work perfectly but I would like to repair the input on channel one someday soon. I really need a differential probe. Can you make a more nuts and bolts explanation of this topic. Its really my biggest downfall in my oscope knowledge. I get certain fundamentals but when putting in real time practice with bridged, stereo, and other variations of where and what to hook up or to use ground leads. I hoped me f’ing it up would have taught me the lesson so I am currently irritated I could never grasp the concept on how applications will vary depending on you wanna introduce yourself into the circuit.

Much as I watch these I'm still confused. I'm in a late 1920's house with 2 wired outlets, where the only tie to earth is at the breaker box where (I suppose) neutral is wired to a water pipe. I surmise THIS represents ground, where neutral and Earth are at the same potential, But that's as far as my brain goes if even correct. I can't understand what that means or how to use it safely? All my three prong devices go either into the adapter (cheater) plugs or into a surge strip which itself goes into an adapter plug. Any helpful tips?

This is why you use a differential probe right ?

Never float your scope, only the DUT!

Safety First

How is your recovery going? From one to another. ❤

it's not the voltage that will kill you considering that when you get a static shock it's probably 2kv BUT pico amps or less. It's current that will kill you. .5 amps across the heart will do it.

This guy's shirt is awesome :D

Great video, but bottom line never have a scope floating. 👍

Ooh, a killer queen plug!

Now subscribing and hitting that bell.

I recently bought Hantek 5102p Oscilloscope after years of wait to buy a scope. I have kind of a stupid doubt and don't know who can I ask it to. Suppose if I have an arduino running which outputs 5volt pwm signal at 50% duty cycle and 1kHz frequency. If I connect probes of both the channel to the very same pin of arduino that is outputting 5V pwm. Will it cause any kind of damage to my scope? A simpler way to put that question would be, "Can I connect same signal to two Probes of two different channels simultaneously?"

I have 2 emergency stop buttons on my workbench just in case. Kills all power.

What if you have no earth ground at all?

You know i've seen this video before and daves, but clearly I clearly didn't get the memo, was just working on a power supply and tried probing post rectifying then tried to set up second channel to look at the first and overlap, about a minute later heard a small pop and smelt some burning :). After watching the video I still didn't understand so I went over and probed the shields with my meter which confirmed they were combined together then I realized what had happened. rectified 0v gnd then i tried putting 28v ac in on the same ground (Facepalm). Can't complain though, live and you learn, scope seems ok for now. If i could go back and time id let it happen again hahehhehehe

And like.

Unless, the scope you are using is battery powered. In that case it would be like a battery powered DMM.

My oscilloscope started smoking, I told it to stop, by the time it did it was dead, because I unplugged it.

I avoid buying one for now because I'm a noob at this and don't want and don't have the money to waste in burning one...

KZfaq: John Ward. Isolation Transformers Explained. You DO NOT plug your ‘scope into an isolation transformer. About 10 minutes into the video I’m no expert, but he explains exactly why.

Breaker plugs

Can anyone test this out and give feedback? pursue circuit solver on the playstore!

James Hetfield goes tech :)

Early in your vid, you said that you can isolate a scope using a cheater plug. That is NOT the case! The neutral/common (white) wire is common to all outlets. How is that possible? Think about it. If you CAREFULLY removed the breaker panel cover (not recommended) you would see that all the white conductors are screwed into a common bus, as all the bare ground wires are. If you completely disconnect the mains breaker, you could then safely probe neutral to ground with an ohmmeter. Why would you have to disconnect the mains, you ask. Think about it logically. There is a low resistance from neutral to ground and back again. Simple Ohm's law: low impedance, high current. The solution is to modify an isolation transformer by opening the case and disconnecting the green chassis wire from the secondary winding and insulating it with heat shrink. Just remember that the secondary winding is now truly floating and completely isolated. Your 'Scope is now 'protected.' You, not so much!

This guy sounds like terry davis

Obviously you have never worked on the internals af motor control systems that if you scope is NOT isolated you WILL blow the scope or the drive.

I don't understand what all the talk all over the internet about this is, surely it's simple, the ground/earth lead on the probe should ALWAYS be connected to EARTH! FULL STOP!?!

This is one of the worst, most rambling dis-jointed explanation I have ever heard.