Hi Folks, This discussion of temperature measurement with ADCs has crossed into my professional life and without being too much of a commercial plug just wanted to mention that I support Linear Technology's temp-to-bits family of ICs: LTC2983, LTC2984, LTC2986.
Overview: each part has 3 24-bit delta-sigma ADCs along with low leakage input buffers, excitation sources, an internal mux, and a small linearization engine. They can measure just about any type of temperature sensor and digitize it to deg C or F with really good accuracy. Ultimately accuracy will depend on the sensor, your implementation, environmental conditions, etc. but the parts have a lot of features that help you get the most out of a given sensor. They aren't super cheap (Digi-Key pricing is particularly bad, if you can order from Linear direct it's much better) but they are to my knowledge by far the simplest way to interface to a thermistor, RTD, thermocouple, etc. and get <1degC accuracy. Ping me off-list if you want to know more or have an application question in mind. -Logan http://www.linear.com/product/LTC2983 On Wed, Jun 7, 2017 at 8:04 PM, jimlux <jim...@earthlink.net> wrote: > On 6/7/17 7:35 PM, Bob kb8tq wrote: > >> Hi >> >> Metal actually makes things a bit worse since it has a lower thermal >> resistance than glass. >> This is also why a high performance dewar is made from glass rather than >> metal. Yes, you >> can go to weird stuff like titanium (it has been done). You can’t afford >> that …. >> >> If you fill the entire dewar with a heat conductor you make things worse >> still. The idea is to >> *block* heat flow out of the heated area. Even without fill, the wall of >> the dewar goes from the outside >> world to the heart of the heated area. It is the perfect “sneak" path >> into the oven. Actually >> it’s not that much of a sneak path since it’s a well known effect :) >> >> Again, none of this is particularly original. Take a hammer to any dewar >> based OCXO and >> the details are going to be similar. >> >> > And the wires provide a thermal path - you've got to get power to it and > the oscillator signal out. > > In dewar OCXOs (like the USOs made by APL), the leads are essentially the > only thermal path in/out. > > > BTW, you don't want to do oil filled. All oil filled electronics (unless > welded closed) inevitably leaks, oozes, or otherwise puts oil on the > outside. If you *must* have oil, then use solid, uninsulated wires to > penetrate the surface of the oil. Otherwise you'll gain new appreciation > for what capillary action is. > > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/m > ailman/listinfo/time-nuts > and follow the instructions there. > _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.