EEVblog #279 - How NOT To Blow Up Your Oscilloscope!
Why Electrical Engineering Stack Exchange recommends it
Electronics Stack Exchange users link it whenever someone asks about scope grounding, probing mains-powered or non-isolated circuits, or has just blown something up with a ground clip.
Recommended by 14 people across 15 different months, 2015 to 2023.
What it is
EEVblog #279 is a 24-minute tutorial by Dave Jones on why an oscilloscope's ground clip is connected to mains earth, and what happens when you clip it to a circuit that is not at earth potential. It covers floating and earth-referenced equipment, isolation transformers and differential probes, with bench demonstrations.
What people said
Strong rec gstorto · 2015-02 · Electrical Engineering Stack Exchange · on “Questions about advanced use of oscilloscope”
The first think I would recommend to a noob in oscilloscopes is this amazing video from Dave Jones (How not to blow your oscilloscope): [this video] Even some novice electrical engineers (like me) have made this mistake. As you are not in the area, this is a must see.
Strong rec Leonardo Bernardini · 2017-09 · Electrical Engineering Stack Exchange · on “Grounding and unisolated power supply”
also, for the ones that would like to understand ground reference, ungrounded, floating ground and all those concepts, I've found this video, that even talks about an oscilloscope, it's EXTREMELY clear and useful, and tells you how to avoid to blow up your lab and/or yourself ;) [this video]
Strong rec Bimpelrekkie · 2019-09 · Electrical Engineering Stack Exchange · on “Oscilloscope and Electrical Safety”
Dave from the EEVBlog made an excellent video explaining about ground and scopes. You should watch it and that might answer your questions. Here's the video: [this video]
Strong rec tlfong01 · 2022-05 · Electrical Engineering Stack Exchange · on “Beginner Electronics Hobbyist Q re: oscilloscopes and grounding”
This video is a must watch for scope newbies: EEVblog #279 - ***How NOT To Blow Up Your Oscilloscope!*** [this video]
Recommends Transistor · 2016-01 · Electrical Engineering Stack Exchange · on “Oscilloscope and main earth reference”
I had a look at the EEVblog [this video] video, thanks. At 7:40 he shows isolation as I have sketched it in my answer. At 23:00 he discusses isolation transformers for both circuit under test and oscilloscope and advises against floating the scope for safety reasons. However, I understand that people do it.
Recommends Marko Buršič · 2016-04 · Electrical Engineering Stack Exchange · on “Power cord without ground cable”
This is rudimental way to measure mains AC line signals when you are poor (like me) and you don't have money to buy differential probe. But it is a kind of shock hazzard. The probe clamp is grounded (yes connected to that missing wire) and if you touch a potential that is referenced to the earth, you make a short. Old school is to use a isolation transformer, bit since a transformer (old scopes) is yet inside you can disconnect ground and have floating scope, means anything you connect with probe clamp you have on metal case, including live wire. For the normal operation I suggest you to wire back the ground wire and buy a differential probe if you indend to measure on the mains. Here is a b
Recommends Ryan Griggs · 2017-04 · Electrical Engineering Stack Exchange · on “Oscilloscope ground lead - BANG!”
I just experienced a big bang caused apparently by a short through my oscilloscope's ground lead, and wanted to see if you could shed light on the why this happened. Yes I have watched Dave's video [this video] on the subject of scope ground leads, and was trying to be very careful. But obviously not careful enough. :-/ I was diagnosing a washing machine control board. I wanted to view the tachometer output pin's status while in operation to see if it was working properly. The tachometer (optical sensor) is powered by 13VDC, provided by an on-board power supply. I connected the oscilloscope ground clip to the 13VDC ground. This is indicated in the schematic below. I connected the oscilloscope lea
Recommends David1 · 2018-01 · Electrical Engineering Stack Exchange · on “Learning the Art of Electronics - diode clamp”
Thanks EE_socal. That makes sense, but just to check I understand properly: the scope probe ground is connected to mains supply earth; the power supply has a choice of mains supply earth or "COM" (not earthed); and the function generator ground is also not earthed. Having watched EEVblog #279 - How NOT To Blow Up Your Oscilloscope! I think it's all right to connect these together but just wanted to check.
Recommends Sredni Vashtar · 2018-04 · Electrical Engineering Stack Exchange · on “Why am I getting a half-wave rectified output when i am using a full-wave rectifier?”
They are not separated. They are the same GND, actually, your home ground. You might want to see this: [this video]
Recommends Jeroen3 · 2018-07 · Electrical Engineering Stack Exchange · on “Oscilloscope ground-probe causing test circuit to malfunction”
I assumed it may be related to earth fault current, but both equipment supplies are properly earthed. You cannot connect oscilloscope ground to anything that is not at mains earth potential. You will get the following short circuit through your oscilloscope: simulate this circuit [LINK] – Schematic created using CircuitLab [LINK] I recommend this EEVblog episode: EEVblog #279 - How NOT To Blow Up Your Oscilloscope! [this video] (since you are lucky the diode failed first) I must add that measuring on these live circuits is dangerous. You are supposed to use an active high voltage differential probe. A Tektronix P5200A for example. There are also many other solutions to evade this problem, but sin