but because PT2 or whatever is called tube if not properly heated and filled with ice crystals
This is not applicable to the problem that is being discussed. It might lead one to conclude that adding more heat would solve the problem. It's the residence time of the crystals against the probe. I liken it to light snow bouncing off a car windshield until you heat the windshield and a light layer of water-slush needs your wipers to become clear.