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Shock from Oscilloscope ground clips

okbro

Member
hello,
I am getting shock, feel small electricity when i accidentally come to touch with the oscilloscope ground alligator clips. I am not sure why this is so, any suggestion what I can do and the cause of it?

thank you
 

For The Popcorn

Active Member
Let's ask the question– what kind of scope is it? And what kind of power cord does it have?
 

rjenkinsgb

Well-Known Member
Most Helpful Member
The neutral line is grounded at the source substation or transformer, but that should be just as well isolated from appliance metalwork as live.
The ground pin is the safety ground.

Can you check for continuity between the scope probe ground and power plug ground pin (without it being plugged in to a power socket)?

If there is no continuity, either the scope has a "ground isolation" jumper disconnected or the power cable / scope have have a serious problem.

If it does have continuity, the problem is either in the power outlet or the general house wiring.
 

okbro

Member
The neutral line is grounded at the source substation or transformer, but that should be just as well isolated from appliance metalwork as live.
The ground pin is the safety ground.

Can you check for continuity between the scope probe ground and power plug ground pin (without it being plugged in to a power socket)?

If there is no continuity, either the scope has a "ground isolation" jumper disconnected or the power cable / scope have have a serious problem.

If it does have continuity, the problem is either in the power outlet or the general house wiring.
there is continuity between scope probe ground and the neutral pin of the power cord(three pins) as shown in image.
images.jpg

is there then a way to check the power outlets or house wiring?how serious is this situation?
 

For The Popcorn

Active Member
Measuring AC voltage between round ground pin and the taller rectangular slot at the oitlet should be close zero. Measuring between the round ground pin and the shorter slot should be close to 120v. Measuring between the two rectangular slots should also be close to 120 volts.

Use caution making these measurements. The test leads will be live. Don't touch the metal parts or allow the metal parts to contact other objects.
 

Dick Cappels

Active Member
I had that problem a couple of days ago. It turned out that the ground pin of the AC outlet that the scope was plugged into was not connected to earth. Moved to another plug and it is no longer painful to use the scope.
 

Diver300

Well-Known Member
Most Helpful Member
there is continuity between scope probe ground and the neutral pin of the power cord(three pins) as shown in image.
View attachment 137303
is there then a way to check the power outlets or house wiring?how serious is this situation?
Your profile says that you're in India. I would not have expected the American plug that you have shown.

You should get a lead that plugs directly into the wall socket, without an adaptor, because some adaptors don't connect the earth wire. What type of sockets have you got?

I would expect a round pin socket and you should use a lead like this:-
SO-1625_ml.jpg

If your oscilloscope was delivered with a lead that has an American plug, and the IEC socket in your picture, you should use a different lead if you don't have American sockets.

One way to check the power outlets is to measure the voltage between all of the pins. You should measure:-

Live to Neutral:- between 220 and 250 Vac
Line to Earth:- between 220 and 250 Vac
Neutral to Earth: less than 2 Vac
 

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