Re: RTD linearization

On Mon, 14 Dec 2009 22:10:22 GMT, Jan Panteltje
<pNaonStpealmtje@xxxxxxxxx> wrote:

I wrote:
All good and well, but when measuring temperature I would think you wanted a low thermal mass
to get fast response?

I have LM135 in an old SMD plastic tube filled with silicone kit, outside,
1 meter from the ground, about 10 cm from the wall, hanging from the wire.
Been working now OK for 10 years or so.
Nice defined output voltage versus temperature.
You can calibrate those too.
But you really do not need better accuracy then 1C... ever.

But I am an artiste!



And I want to add something to that.
All that talk about measuring to .x digits temperature (substitute for 'x'
what you had in mind), will really look funny when:
The sun shines on your outside sensor, and the temp is all of the sudden 20 degrees to high.
Hail falls on it, and starts melting, and it insists it is zero C.
Snow, rain, so:
You need a very good place, shielded from wind, sun, away from hot walls,
other radiating objects, at the correct height.

I have been measuring outside temp now for many years, and seen some very funny readings.

I plan to put the outdoor sensor (1K RTD in a plastic tube, epoxy
filled) on the north side of the cabin, in the niche under the stairs
where the gas meter (and all the old skis) is stashed, exposed to the
world but protected from rain and snow. The adjacent wall is concrete
blocks, the wall of the unheated garage.

Response speed isn't much of an issue here.

John

.

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