Hi Neil,

I've been impressed by the response speed of tiny thermocouples. Their
response is on the order of a second. I'd say that it is on the order
of 20 seconds for typical semiconductor temp sensors.

RTDs are probably in the same range as thermocouples but tend to be
more expensive I think.

I have seen to-92 packaged temp sensors from National which list
thermal response time in their graphs section. The response is roughly
exponential, like an RC circuit with a step input, so the graph should
give you the time constant (at which time the temp difference is
reduced to 37% of the original difference).

You could also possibly greatly increase the response speed of any
temp sensor by mounting it to a small heatsink and blowing air over it
with a small fan.

Sean

On Wed, Jun 25, 2008 at 12:13 AM, PicDude <picdude2@avn-tech.com> wrote:
>
> I'm searching for a fast temp sensor for measuring ambient air temperature
> (with some overhead) -- say -10deg-C to 120deg-C.  1% accuracy or better.
>
> There are a lot of sensors that meet this numerical criteria, but what types
> of temps sensors are *fast*?  I usually don't see response time listed in
> the datasheets (and not even sure what the parameter is for response time),
> and I don't have a specific value for how fast it should be, but I want to
> compare various sensor types and start investigating/experimenting with the
> fastest of these.
>
> I did find "fast response RTD's" and wondering how they compare (speed-wise)
> to other alternatives such as semiconductor sensors.  I expect the plastic
> housings for TO-92 types and similar would be enough of an insulator to
> significantly increase the response time.  Will the metal can versions
> (TO-39 IIRC) be considerably faster?  Open element sensors and low-mass
> sensors should be fast.  But I'm sure I am missing a lot of other
> possibilities here.
>
> Any links/clues on this?
>
> Thanks,
> -Neil.
>
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