Can anyone explain how to measure the insulation resistance of an isolated SMPS PCB?

Is it correct to tie ACL and ACN and apply one terminal there, and the second terminal goes to the ground of the secondary part of the circuit? or Do I need to test between ACL-ACN, ACL-Secondary Ground, ACN-Secondary Ground? Do I need to test ACN-to the plastic enclosure of the PCB as well, or is it only needed for AC Dielectric Withstand Test?

I am using Farnell's brand Megohmmeter(looks like rebranding from uni-t)

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    \$\begingroup\$ What insulation test spec are you working to and what does that document tell you? \$\endgroup\$ – Andy aka Apr 22 '17 at 8:42
  • \$\begingroup\$ I am preparing for EN 60950-1:2006 class II. I've recently started to read the document. It just located that I need a Hi-pot test for 1 min (and 2 sec on the production), but I haven't read how it needs to be done yet (if it should be AC or DC - but as I read on the Net, it says it should be AC). \$\endgroup\$ – Angs Apr 22 '17 at 8:53
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    \$\begingroup\$ so... Read? Why should we paraphrase a standard that you have lying in front of you, and that you will have to adhere to by the letter? I mean, absolutely feel free to ask for clarifications of things in the standard that you don't understand, but I don't see why we should write something that you already have in front of you, written. \$\endgroup\$ – Marcus Müller Apr 22 '17 at 9:14

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