repair of evaporator core

I have 1996 Accord. I am setting up a new evaporator core and I have fitted the copper temp. sensor (that runs from the expansion valve) have fit the sensor, just like the original, flat against the low side pressure a/c line that is inside the evaporator core plastic box.

My question is, Its been a few days since I took this apart and I may have forgotten specifics about proper insulation of the sensor. As I rember, the sensor was right up against the line and glued in such a way as to have no glue or insulation in between direct contact of the copper sensor to aluminum tube? I believe it was then wrapped externally with a rubber insulation material similar to the sealing material on the evaporator core box. Is this correct or does the sensor lie against the line without insulation? Is the purpose of the sensor to measure the temperature of the low side aluminum line or does it measure the ambiant temperature of the air inside the car?

P.S. the old evaporator core was really dirty and had alot of clogged fins. Any tricks to avoid this in the future with the new one? Probably vacuum the car more often! Thanks for your replies.