Electronics > Beginners
Should I float a scope on a car
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Seamus16:
This is a very basic question. I have had a search but cannot find anything relevant.

I want to check the K-Line on the OBD2 connector on my car since none of the plugs I am using can make connection.

I want to put an analogue scope on it to check if it is working. I have been arguing with myself and now think I should run the scope off an isolation transformer.

Can anyone confirm please

Regards

David
JS:
The car is floating by itself, while I don't know the best practice you could ground the car to what you want. I have to do a similar thing to a boat but it has a dedicated connection to the water so it gets a bit trickier...

Also, breaking the ground connection of the scope should leave the thing floating, this is widely used but not recommended. The best way is to have a differential probe, in some cases you want a isolated probe, like low signals in high level common modes.

At the end of the day you will probably want a pair of a bunch of different probes so you end with more money in probes than scopes...

JS

RoGeorge:
Why floating the scope?
Isn't the car at a floating potential already?

Are there any other power grid powered devices (like the oscilloscope is power grid powered) that are connected to the car?
If either the oscilloscope or the DUT is floating, then there should be no problems.
Seamus16:
Thanks to you all.

I thought it was floating but when you attach the scope to car earth I thought it wouldn't hurt to ask.

I don't really need any data of it but just want to know that there is a signal there. The voltage does not tie in with what I was led to expect.

Benta:
NEVER float test equipment. Float the device under test (DUT). And your car is already floated.
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