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multiple engine leads from one source

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TimRhod(at)aol.com
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Posted: Sat Nov 25, 2006 2:07 pm Post subject: multiple engine leads from one source

Does anyone know if you can pull multiple leads off of CHT probes, EGT  probes,  and Oil Temp  to feed two different engine analysis systems.  I have  a Vision Micro system VM1000  and now a new Grand Rapids EIS.  I would Like to use both as back up but would also like not to have to install  duplicate CHT, EGT, oil temp Probes.   Thanks Tim  

  [quote][b]

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nuckollsr(at)cox.net
Guest

Posted: Sat Nov 25, 2006 3:52 pm Post subject: multiple engine leads from one source

At 05:05 PM 11/25/2006 -0500, you wrote:



 	  Quote: 	
		  Does anyone know if you can pull multiple leads off of CHT probes, EGT 

probes,  and Oil Temp  to feed two different engine analysis systems. I 

have  a Vision Micro system VM1000  and now a new Grand Rapids EIS. I 

would Like to use both as back up but would also like not to have to 

install duplicate CHT, EGT, oil temp Probes.   Thanks Tim


	


   You can . . . IF.



   It's dependent upon the signal conditioning circuitry in

   the two instruments. Some systems will tolerate paralleling

   as you've suggested but without seeing schematics of the

   two systems and/or talking with the designers, it's not

   possible to make a recommendation.



   Bob . . .

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stein(at)steinair.com
Guest

Posted: Sat Nov 25, 2006 7:08 pm Post subject: multiple engine leads from one source

Hi Tim,

  

 With some probes yes, and others no.   The most likely answer to your question is no.  I'm a bit confused to begin  with why you have 2 engine monitors (both have quite a good history of  reliability) with GRT having literally THOUSANDS of those units flying with  little to know problems that I've known about.  Splicing CHT's & EGT's  could be a slippery slope...there are many different kinds of wire & probes  between mfgrs (such as shielded/unshielded, grounded/ungrounded, solid/stranded,  etc..).  All are setup to read certain specifics.  Paralleling onto  them could cause lots of problems.  Some transducers however allow you to  split their signals.  It's much easier on powered/excited probes than plain  old resistive ones.  In basic resistive probes if you "tack on" other  things it can significantly vary the readings...

  

 Hope that helps.  In the end I'd just  say stay away from that and decide which engine monitor to use.  Two of  them is frankly a bit of overkill in my opinion.  If the fan is turning  you're most likely ok   Duplicate CHT's & EGT's don't buy you much -  you can't possibly watch all of each systems indications all the time  anyway.  If they don't match, now you have to try and decide which one is  the "master" or is "right".  If you're doing this when you have a problem  then you're not flying the plane.

  

 Anyway, enough of my bantering.  I get  this question asked with surprising regularity and I still can't figure it  out!   Sorry for being sarcastic, that's not my intent.  I'm just  trying to point out that with added complexity comes reduced reliability and  little gain in form or in function.

  

 Cheers,

 Stein.

 [quote]   --

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TimRhod(at)aol.com
Guest

Posted: Sat Nov 25, 2006 8:06 pm Post subject: multiple engine leads from one source

Thanks for the input  Tim 

  [quote][b]

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ainut(at)hiwaay.net
Guest

Posted: Sat Nov 25, 2006 8:33 pm Post subject: multiple engine leads from one source

You know the old saying: never use just 2 watches...



David M.

Stein Bruch wrote:



[quote] Hi Tim,

  

 With some probes yes, and others no.  The most likely answer to your 

 question is no.  I'm a bit confused to begin with why you have 2 

 engine monitors (both have quite a good history of reliability) with 

 GRT having literally THOUSANDS of those units flying with little to 

 know problems that I've known about.  Splicing CHT's & EGT's could be 

 a slippery slope...there are many different kinds of wire & probes 

 between mfgrs (such as shielded/unshielded, grounded/ungrounded, 

 solid/stranded, etc..).  All are setup to read certain specifics.  

 Paralleling onto them could cause lots of problems.  Some transducers 

 however allow you to split their signals.  It's much easier on 

 powered/excited probes than plain old resistive ones.  In basic 

 resistive probes if you "tack on" other things it can significantly 

 vary the readings...

  

 Hope that helps.  In the end I'd just say stay away from that and 

 decide which engine monitor to use.  Two of them is frankly a bit of 

 overkill in my opinion.  If the fan is turning you're most likely ok 

   Duplicate CHT's & EGT's don't buy you much - you can't possibly 

 watch all of each systems indications all the time anyway.  If they 

 don't match, now you have to try and decide which one is the "master" 

 or is "right".  If you're doing this when you have a problem then 

 you're not flying the plane.

  

 Anyway, enough of my bantering.  I get this question asked with 

 surprising regularity and I still can't figure it out!   Sorry for 

 being sarcastic, that's not my intent.  I'm just trying to point out 

 that with added complexity comes reduced reliability and little gain 

 in form or in function.

  

 Cheers,

 Stein.



     --

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