At 10:36 AM 11/10/2004 -0500, you wrote:

Al Gietzen wrote:

Subject: [FlyRotary] EGT sensors


Time to change the EWP subject:)
At the rotary roundup Tracy mentioned that if you have two EGT sensors, you
can tune each rotor separately. Does anybody have two EGT sensors, how they
are mounted and where do you get them?
Bulent
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I have three (20B) inconel clad K-type, clamp-in.  One in each header a
couple inches from the port.  Got mine from Grand Rapids Technologies, but
you may alos be able to get them from Omega.  They are built into a hose
clamp so you drill the hole, tighten the clamp, seal up tight.

Al

Don't you mean J-type? I believe K is lower temperature.

        The opposite is true.

         The ASTM recommends that type J be used continuously only to 760 C (1400 F). Type K are rate for continuous use up to 1260 C (2300 F).

        With modern metering, type K thermocouples are superior to type J. The copper lead in type J is a high thermal conductor that transports heat to (or away) from the tip, resulting in increased error in the measurement. The copper also oxidizes easily. Copper oxide has an enormous Seebeck coefficient, so the calibration goes out the window if the wire or the connections corrode.

        The main reason that type J was popular was that it has a very flat Seebeck coefficient (as a function of temperature.) This makes the temperature (roughly) proportional to the voltage over a pretty good range. The Seebeck coefficient for type K varies quite a bit with temperature. This makes it hard to build a simple analog readout, but is not a problem for a modern electronic readout.

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