OSCILLOSCOPE SAFETY ALTERNATE METHOD - Page 1
Forum section: electronics / testgear

author: jisake2
author_rank: Newbie
timestamp: February 15, 2024, 03:16:37 pm
content: Relatively new to using an Oscilloscope. After viewing EEVblog#279 video - How NOT to blow up your oscilloscope (and/or High Voltage Oscilloscope Probe), joining the EEVblog. I have over 50 years experience working with VOM's. Now entering into an area I have need of an Oscilloscope.I attached a photo in concept which I believe prevents an exploded probe or worse. Using a stand alone power supply (Trust that will isolate the grounding?) Then using a handheld oscilloscope that is battery powered.Believe the only time common ground could be a factor is if devices are charged with grid power when used. Let me know your thoughts?

author: tggzzz
author_rank: Super Contributor
timestamp: February 15, 2024, 03:37:53 pm
content: Don't forget that the concept of "ground" and "earth" is merely a concept/model that is useful insomecircumstances. Consider, for example, what "earth/ground" means in an aircraft.Basically, it looks like you don't understand themanyways high energy circuits can damage you and/or equipment.If you are going to be working on high energy circuits, then I suggest you read the references given athttps://entertaininghacks.wordpress.com/library-2/scope-probe-reference-material/to find out the different types of scopes and probes, why they exist, and what they do and don't do.Pay particular attention to the anecdote about "someone that took precautions and still killed themself." Understand why HV differential probes can be useful. not all high voltages are high energy: I have school equipment with exposed terminals in the 250-500V range, and a handheld tester that puts out 3kV. Similarly some high energy circuits are low voltage: consider shorting out a car lead-acid battery

author: Ian.M
author_rank: Super Contributor
timestamp: February 15, 2024, 03:58:11 pm
content: Instead of killing your scope, you may kill yourself!Many handheld scopes are unsafe if the probe ground is clipped to a high voltage node. Anything that lets you touch the metal BNC connector, or has a metal or part metal case is unsafe for floating use >50V. The ones you can do this safely with are generally scopemeters with fully shrouded probe connectors and a Cat II or better rating.

author: J-R
author_rank: Super Contributor
timestamp: February 15, 2024, 08:43:05 pm
content: Depending on the probes and the voltages involved, you can use two channels on your scope along with math to act as a pseudo-differential probe. Observe the maximum probe voltage limits (typically under 600Vp-p) and of course don't connect the scope probe grounds to the device under test.Better option is to buy a high voltage differential probe. I have the DP20003 and it's passable:https://www.micsig.com/Differential%20Probe04/

author: csuhi17
author_rank: Frequent Contributor
timestamp: February 15, 2024, 09:57:32 pm
content: +1 vote for the differential probe.It's not that expensive these days, Micsigs are around 200 USD. I think the person's safety is worth that much.My method for maximum 500V AC measurement without Diff probe is that.1. I use only one channel of the hand scope.2. I insulate all the others with a rubber cap.3. I only use a suitable probe, which was designed for this purpose.Insulated BNC connection and the correct design for the measuring needle.https://www.ebay.com/itm/134466286896?Thanks coromonadalix, I didn't know that the Ebay link was only needed up to the question mark. I'm always learning something new4. The grounding of the BNC and the grounding of the calibration square signal and, if there is one, the grounding of the built-in AWG are connected! You also have to insulate them properly!