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CHT/EGT connectors

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rsmith52

Joined: 16 Mar 2017
Posts: 15
Location: Crawford, CO

Posted: Sat Dec 09, 2023 7:45 am Post subject: CHT/EGT connectors

There is a local A/P that insists that special connectors are needed for CHT/EGT probes to prevent dissimilar metal problems affecting the readings. My Alcor probes have PIDG ring terminals and I purchased PIDG ring terminals for making connections to the thermocouple wires, with the provided screws and nuts. The PIDG terminals all look like they are made from the same material. I'm thinking I don't need to spend about a $100 for these special Prosense Type K Thermocouple connectors.

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recapen(at)earthlink.net
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Posted: Sat Dec 09, 2023 8:29 am Post subject: CHT/EGT connectors

You should use the same style/type/brand as those provided on the probes.

Is this for a certified aircraft or EAB?  If certified, are the probes

TSO'd?



--

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racerjerry

Joined: 15 Dec 2009
Posts: 202
Location: Deer Park, NY

Posted: Sun Dec 10, 2023 4:28 am Post subject: Re: CHT/EGT connectors

I'm no expert, but I guess the A & P was speaking about errors introduced by an extra "cold junction" introduced into the system.  My GUESS is that the error would be insignificant as long as the "junction" temperature was not too far from ambient.



Might be interesting to do a side by side experiment .



We are generally not too interested in absolute accuracy with CHT / EGT readings.

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Jerry King

rsmith52

Joined: 16 Mar 2017
Posts: 15
Location: Crawford, CO

Posted: Sun Dec 10, 2023 7:27 am Post subject: Re: CHT/EGT connectors

This is on my Experimental. I have no idea what brand of PIDG Alcor used. The ones I purchased look identical. The A/P said these connectors are used on all new planes.

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Eric Page

Joined: 15 Feb 2017
Posts: 247

Posted: Sun Dec 10, 2023 8:45 am Post subject: Re: CHT/EGT connectors

 	  rsmith52 wrote: 	
		  I have no idea what brand of PIDG Alcor used. The ones I purchased look identical. 	


PIDG (Pre-Insulated Diamond Grip) is a trademark of TE Connectivity.  They're the only manufacturer of genuine PIDG terminals.

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nuckolls.bob(at)aeroelect
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Posted: Sun Dec 10, 2023 5:19 pm Post subject: CHT/EGT connectors

At 09:45 AM 12/9/2023, you wrote:

  	  Quote: 	
		  --> AeroElectric-List message posted by: "rsmith52" <rodsmith52(at)yahoo.com>



 There is a local A/P that insists that special connectors are needed for CHT/EGT probes to prevent dissimilar metal problems affecting the readings. My Alcor probes have PIDG ring terminals and I purchased PIDG ring terminals for making connections to the thermocouple wires, with the provided screws and nuts. The PIDG terminals all look like they are made from the same material. I'm thinking I don't need to spend about a $100 for these special Prosense Type K Thermocouple connectors. 	




 

   You're right.  If you're not needing ease of de-mating

   for maintenance, the PIDG/nut-n-screw will produce

   error free performance. You could also consider PIDG/

   M-F FastOn terminals. Of course, the junctions should

   be covered with heat-shrink. This is why you can take

   a thermocuple pair through a 'generic' connector (4-quad

   crimped pins preferred.



   To be sure, you're mechanic is half right . . . dissimilar

   metals used in the thermocouple conductor WILL generate

   parasitic, thermally dependent couples which CAN generate

   errors in measurement of the TARGET couple on the engine.



   However, the parasites can be arranged in PAIRS and

   electrically polarized to oppose each other; 

   the errors are washed out. This presumes that

   your t/c wire on BOTH sides of the joint.



   No 'special' connectors necessary. However, there

   ARE inexpensive connectors specifically designed

   to mate T/C wire runs.



  https://tinyurl.com/ymjvhnhw 



   Widely available from electronics and instrument

   supply houses. These can be secured with an

   short hunk of heatshrink.



 

   Bob . . .



                    //// 

                   (o o) 

    ===========o00o=(_)=o00o========= 

    < Go ahead, make my day . . .   > 

    < show me where I'm wrong.      > 

    =================================

  

    In the interest of creative evolution

    of the-best-we-know-how-to-do based

    on physics and good practice.

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nuckolls.bob(at)aeroelect
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Posted: Wed Dec 13, 2023 1:20 pm Post subject: CHT/EGT connectors

At 09:27 AM 12/10/2023, you wrote:

  	  Quote: 	
		  --> AeroElectric-List message posted by: "rsmith52" <rodsmith52(at)yahoo.com>



 This is on my Experimental. I have no idea what brand of PIDG Alcor used. The ones I purchased look identical. The A/P said these connectors are used on all new planes.



 	


   Forgive me . . . 'PIDG' is a trademark of

   AMP, Inc., a legacy manufacturer of wire

   termination products going back nearly

   100 years. It stands for "PreInsulated

   Diamond Grip" . . . a reference to the

   3-piece, wire grip feature of this class

   of terminal. In fact, dozens of companies

   manufacture equivalent devices conforming

   to military specification MIL-T-7928.



   'PIDG' has become the common name for the

   technology sorta like 'XEROX'. It

   represents the-best-we-know-how-to-do

   in mating a wire with a variety of terminations.



   The way you can tell a true PIDG device

   from knock-offs is the existence of

   a copper sleeve over the wire grip and

   under the insulation grip as shown in

   the attached illustration.

  



 

 

   Bob . . .



                    //// 

                   (o o) 

    ===========o00o=(_)=o00o========= 

    < Go ahead, make my day . . .   > 

    < show me where I'm wrong.      > 

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    of the-best-we-know-how-to-do based

    on physics and good practice.

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