Wetbulb and drybulb reading

[Slade Smith]

Thank you in advance.. I have a psychrometer and it says that i can test the wb and db of the return and supply..How am I to measure? should I drill a hole at the end of the return and at the beginning of the supply to get the reading?:cool:

[chillbilly]

I check my wetbulb inside the insulated structure's envelope, usually at the return air filter grille area and then in an area where there is the most supply air.
I take d/b temp splits inside the plenums.