I just got two of these Exo Terra temperature monitors. The type that has a dial (not digital). I notice it came with a round double sided tape to put onto the glass etc. and in the middle of the back, there is a metal knob. Does it detect the heat from that metal knob? Because it seems that my heat source may be heating the plexiglass more so than the air inside that area per se, and I don't know if it is the heat on the plexiglass that is being measured or the actual temperature of the air.