On Tue, 24 Jun 2008 21:13:44 -0700 (PDT) PicDude wrote: > But I'm sure I am missing a lot of other > possibilities here. One of the most important factors you didn't mention is thermal resistance. If the sensor is in free air, it'll take much more time than when it is in contact with the thing to measured. It's very much like a when you need to cool with heat sink, just the other way around. If you can make the sensor have contact with the object you'll have much better speed with metal housings. Else (air contact) it'll be pretty much the same, and the time constant will mainly depend on the sensor's mass and air circulation. John -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist