I am sorry, I don't get it...

what is the KH reference solution? Is it a fluid with a known KH? or an indicator reagent that tells you the KH?
and what about the air gap and pH meter?

you put the pH meter in the KH reference solution? But will the KH reference solution not have a pH which is totally independent of the tank's pH?

And so and so on... basically I don't get it...

maybe a picture/drawing will make much clear?

greetz,

yme