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Date: Fri, 12 Nov 2004 10:04:45 -0500
From: Finn Lassen <finn.lassen@verizon.net>
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To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Subject: Re: [FlyRotary] Thermocouples (was: EGT sensors)
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Sorry, I stand (sit) corrected.

Finn

Bill Dube wrote:

> 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
>>> -----
>>> 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.
>
>
>
>>>  Homepage:  http://www.flyrotary.com/
>>>  Archive:   http://lancaironline.net/lists/flyrotary/List.html
>>
>