I needed a fast temperature sensor for water temperature control and compared a couple of promising thermistor models. I thought I'd share the results here. Vishay NTCAIMME3 is the winner, it has a time constant of 1.1 sec according to my measurements and is quite inexpensive for an encapsulated sensor. Amphenol CR1 is a bare chip coated with water resistant coating. But despite having a much smaller mass, it actually has a slightly slower thermal response.