Another way to go is to buy a Capacitor Discharge Tester that is made to
perform the test you want.  Just plug it in and press a couple buttons.
There may be more on the market but the only one I know of is made by
Compliance West USA, model CDT-240.  We have the 15 amp version.  The nice
thing about this is you just plug it in, select the standard and test you
want to test to, then start.  Simple and safe.

On our products, we find that the load of the product itself discharges the
"X" caps very quickly. Worst case is when the power switch is OFF and the
RF Line Filter is still connected to the AC Mains. Most line filters have
adequate bleeder resistors to discharge the caps to a safe level within the
5 seconds (or whatever standard you are using).  But some of the larger
line filters used in industrial equipment (typically permanently mounted)
do not discharge their caps fast enough.  So this is always a good test to
run.

Hope this was helpful.
The Other Brian

On Mon, Oct 17, 2022 at 11:18 AM Scott Xe <scott...@gmail.com> wrote:

> In order to judge if there is no risk of electric shock from charged
> capacitors, it is required to measure the voltage across L and N of mains
> plug after the removal of power input.  To avoid grounding loop between
> test equipment and the unit under test, an isolating transformer is
> strongly recommended.  I have learnt another way by using Add Function and
> two hot probes of a dual channel DSO.  Can someone advise which way is more
> common in safety conformity test.  Especially the latter one, I have not
> tried it yet before and appreciate any notes I must take in the measurement.
>
> Thanks and regards,
>
> Scott
>
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