[chbot] Earth issues

[Mark Beckett]

The one thing that frightens me here, is that the mains powered scope 
has had it's earth removed.
It was designed to have an earth for safety.

Earth it and then work out what circuits will be affected by placing an 
earthed scope probe onto them.
Generally a capacitor in series with the earth side of the probe will 
allow AC voltages to be seen, but possibly not measured correctly.

There is no earth on a Laptop, and therefore you can have bad situations 
occur.
You can easily earth the metal contact point to ensure it doesn't float.

Mark

Marshland Engineering wrote:
> Ok not Kaiakora type but electrical ones.
>
>
> I have a digitally controlled soldering iron, PSU and Scope. For the past XX
> years, I never connected the scope earth to the plug earth thinking that the
> probe ground would therefore float with reference to my power supply earth. 
>
> Any way, when soldering components on my test PCB, a few LED's started to
> glow. I measured the voltages on the test equipment and I had 90 volts between
> my soldering iron and scope probe earth. A few more measurements and I found
> scope probe earth was the problem. 
>
> What is normal? Earth the scope, disconnect all cables to the board before
> soldering, run an isolating transformer?
>
> Often USB powered boards get supply from the PC and some laptops only have 2
> pin plugs so all sorts of earth issues can occur? 
>
> Any suggestions ? 
>
> Just ordered a battery pocket scope from Aliexpress. That will solve one
> issue. 
>
> Cheers Wallace.
>
>  
>
>
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