On Tue, 28 Oct 2008 06:26:14 -0700, scottandrewalexander wrote:

Most of all, I'm real interested to find out if anyone has installed one
and noticed a tempeture change when entering a thermal?

Its normal to use a sensitive thermistor-based temperature sensor to find
thermals when flying Free Flight duration models in a contest. The usual
temperature swing when a thermal blows through is about 1 degree
Centigrade though it can vary from 0.5 to 2 degrees depending on weather
etc. with the measurement made at around 5m. Secondly, you need a fast
response, which means a very small thermistor bead (no bigger than 0.8mm
diameter and under 0.5 mm is preferable) and it must be a naked bead -
common units which enclose the bead in plastic or metal probes are
useless because their response lags the actual temperature change by
anything up to 30 seconds.

I've never made or heard about comparable measurements at flying heights
and would be interested to hear if anybody else has measurements above
ground level. For the moment lets assume the same temperature range is
found at flying height.

Can it be used, in anyway, to help center a thermal? Seek out a
thermal?

You'd need a read-out with a resolution of at least 0.1C to be able to
reliably see the shape and position of a thermal so if your read-out
isn't that accurate you're on a hiding to nothing: my SDI C4 only reads
in whole degrees. Last but not least, its thermistor is buried in a 3mm
diameter plastic housing, so while its fine for monitoring the average
air temp or spotting icing conditions, its response is far too slow to
find thermals: a good vario has a 2-4 sec response, so it follows that
the thermistor-based thermal detector must have a similar response rate.


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
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