Mailing List flyrotary@lancaironline.net Message #6569
From: Russell Duffy <13brv3@bellsouth.net>
Subject: RE: [FlyRotary] Re: EGT/CHT wiring
Date: Wed, 17 Mar 2004 19:31:09 -0600
To: 'Rotary motors in aircraft' <flyrotary@lancaironline.net>
Message
Tracy,
Thanks for the clarification.  I plan on making my own CHT thermocouples by tig welding one end of J-type thermocouple wire and inserting into a 1/8" hole in the rotor housing.  What method would you suggest to keep the sensing end from shorting once inserted into the rotor housing?  Would 1/16" shrink tubing work?

Mark S.  
 
I talked to Tracy about this today, mostly because I made all those J-type thermocouples by just connecting the ends of the wire, but realized that they aren't grounded, and I didn't ground them inside the connector either.  Tracy suggested grounding them at the junction instead.  My reply was something like "I don't see how you could generate a voltage when you're grounding the connection of the two wires".  His reply was to look at a spark plug type CHT probe and notice that they're doing the exact same thing.  I sure can't explain it, but it must work. 
 
I have yet to thoroughly test my homemade ungrounded CHT probes, but at ambient temp, they all read correctly. I'll give them a boiling water test at some point to see how that holds up at higher temps. 
 
Cheers,
Rusty (progressing by deferring everything until later)
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