[chbot] Earth issues

[Charles Manning]

What is normal?

Don't worry about normal. "To measure is to know".

BTW: The scope I have here (Rigol) has earthed probes.

On Tue, Nov 22, 2016 at 2:45 PM, Marshland Engineering <
marshland at marshland.co.nz> 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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