Proper Hygrometer placement

Just something I noticed. Curious as to how you guys do
your readings. Should the hygrometer be placed on the ground like the substrate its self? Or a little higher. I have one sitting on the substrate by my guys hide. It reads 52% humidity. I have one not even a few inches away. It’s 2 inches above the substrate which reads 64% humidity. So which is correct?

I put my on the cage wall. If the snake is one that stays on the ground I will put it a few inches above the substrate. In my arboreal snakes I have them about half way up the wall since they use all the vertical space.

Overall I just watch the humidity in the room but that is a perk of having a snake room.