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Temperature Gauges

Subject: Temperature Gauges
From: Fred Fillinger <fillinger@ameritech.net>
Date: Thu, 12 Sep 2002 21:37:17
In noting discussion re temps, I am wondering if anyone is testing
their temp gauges for accuracy, before drawing conclusion and doing
mods.

---From experience in designing digital readouts from the type sensors on
the Rotax, the issues aren't trivial. If you look at the
resistance/temp chart in the manual, it's nonlinear, with very low
resistance at high temps of critical interest.  Ways around that can
be crude, in a temp gauge at the low prices they sell for.  I have a
high-end automotive temp gauge, with a separate electronics module,
and a sensor of different characteristics which should mitigate the
problems.  It's still only sort of close in accuracy.

The best way I found to check them is a digital meat or candy
thermometer, like only $11.46 at Wal-Mart, but fast acting and very
accurate.  Heat up a small deep-fat fryer to above temp needed,
disconnect from wall current, and immerse (and stir) with the sensor
near the digital probe.  Observe both readings as the oil cools down.

I'm curious if others have tested gauge accuracy to see if the various
experimental-aircraft-only temp gauges, with Rotax sensors, are
accurate within a reasonable definition of the word.

Best,
Fred F.
N3EU


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