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Dennis Jones

Joined: 17 Sep 2006
Posts: 45
Location: Poplar Grove, IL

Posted: Tue Jan 31, 2012 5:05 pm Post subject: Thermocouple leads

I had to increase the length of the thermocouple leads to reach the data processing unit. All six cylinders show abnormally high temps. Could the increase in resistance cause the temperature increase?

berkut13(at)berkut13.com
Guest

Posted: Tue Jan 31, 2012 5:54 pm Post subject: Thermocouple leads

EGT or CHT?



How were they "extended"?



What type of thermocouple?  (K, J, Resistive)



--

mrspudandcompany(at)veriz
Guest

Posted: Tue Jan 31, 2012 5:55 pm Post subject: Thermocouple leads

I had to increase the length of the thermocouple leads to reach the data

processing unit. All six cylinders show abnormally high temps. Could the

increase in resistance cause the temperature increase?



		Dennis,



		Did you use thermocouple wire for the extension?

Thermocouples generate a potential depending upon the temperature difference

from one end to the other.  You must use proper procedure when extending

these wires.



		Roger

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Dennis Jones

Joined: 17 Sep 2006
Posts: 45
Location: Poplar Grove, IL

Posted: Tue Jan 31, 2012 8:33 pm Post subject: Re: Thermocouple leads

Both CHT and EGT. They are thermocouple wire. I used the exact same wire as the equipment came with. I silver soldered the new lead extensions as shown by Bob. I do have a multimeter that will test thermocouple wire however I have not used that feature as of yet. The one test I have not attempted is the check of the indication without the engine running. My studies show that they should indicate ambient temperature.

jason(at)jasonbeaver.com
Guest

Posted: Tue Jan 31, 2012 8:59 pm Post subject: Thermocouple leads

Does anyone know if there are any issues in running EGT/CHT thermocouple wires along side the coax ignition leads from a Lightspeed Plasma II ignition (the lines between the ignition box and the coils)?  My tech counselor said this could be a source of inaccuracy in the temperature reading.



thanks,



jason



On Jan 31, 2012, at 10:33 PM, Dennis Jones wrote:



 	  Quote: 	
		   

 

 Both CHT and EGT. They are thermocouple wire. I used the exact same wire as the equipment came with. I silver soldered the new lead extensions as shown by Bob. I do have a multimeter that will test thermocouple wire however I have not used that feature as of yet. The one test I have not attempted is the check of the indication without the engine running. My studies show that they should indicate ambient temperature.

 

 

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p=365354#365354

nuckolls.bob(at)aeroelect
Guest

Posted: Wed Feb 01, 2012 6:27 am Post subject: Thermocouple leads

At 10:57 PM 1/31/2012, you wrote:

 	  Quote: 	
		  



Does anyone know if there are any issues in running EGT/CHT 

thermocouple wires along side the coax ignition leads from a 

Lightspeed Plasma II ignition (the lines between the ignition box 

and the coils)?  My tech counselor said this could be a source of 

inaccuracy in the temperature reading.


	


    I doubt it very much. The coax is double shielded

    (electro-static coupling ZERO) and the currents

    flowing in the center-conductor (outbound) exactly

    compliment return currents flowing in the shield.



    How much inaccuracy? You said they read high? All

    read high by the same amount? Are your probes isolated

    from engine ground or do they both electrically and

    thermally connect to the engine? Does turning the

    alternator on/off make any difference? Try turning

    EVERYTHING on to make this test. Present the alternator

    with the largest possibible load.





   Bob . . .

mrspudandcompany(at)veriz
Guest

Posted: Wed Feb 01, 2012 7:08 am Post subject: Thermocouple leads

 	  Quote: 	
		  

Does anyone know if there are any issues in running EGT/CHT 

thermocouple wires along side the coax ignition leads from a 

Lightspeed Plasma II ignition (the lines between the ignition box 

and the coils)?  My tech counselor said this could be a source of 

inaccuracy in the temperature reading.


	


    I doubt it very much. The coax is double shielded

    (electro-static coupling ZERO) and the currents

    flowing in the center-conductor (outbound) exactly

    compliment return currents flowing in the shield.



    How much inaccuracy? You said they read high? All

    read high by the same amount? Are your probes isolated

    from engine ground or do they both electrically and

    thermally connect to the engine? Does turning the

    alternator on/off make any difference? Try turning

    EVERYTHING on to make this test. Present the alternator

    with the largest possibible load.





   Bob . . . 



		I believe you are combining 2 questions from different

listers. One extended thermocouple wires and has a high reading and the

other is questioning if running thermocouple next to ignition wires causes

incorrect readings.



		Roger

winmail.dat

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Download

Filename:

winmail.dat

Filesize:

3.87 KB

Downloaded:

465 Time(s)

jason(at)jasonbeaver.com
Guest

Posted: Wed Feb 01, 2012 8:33 am Post subject: Thermocouple leads

I'm not flying yet, so I have no way of testing.  The tech counselor was just speculating that this could be a source of inaccurate readings.



Thanks,



Jason



Sent from my iPhone



On Feb 1, 2012, at 10:04 AM, "ROGER &  JEAN CURTIS" <mrspudandcompany(at)verizon.net> wrote:



 	  Quote: 	
		  > 

> Does anyone know if there are any issues in running EGT/CHT 

> thermocouple wires along side the coax ignition leads from a 

> Lightspeed Plasma II ignition (the lines between the ignition box 

> and the coils)?  My tech counselor said this could be a source of 

> inaccuracy in the temperature reading.

 

    I doubt it very much. The coax is double shielded

    (electro-static coupling ZERO) and the currents

    flowing in the center-conductor (outbound) exactly

    compliment return currents flowing in the shield.

 

    How much inaccuracy? You said they read high? All

    read high by the same amount? Are your probes isolated

    from engine ground or do they both electrically and

    thermally connect to the engine? Does turning the

    alternator on/off make any difference? Try turning

    EVERYTHING on to make this test. Present the alternator

    with the largest possibible load.

 

 

 

 

   Bob . . . 

 

        I believe you are combining 2 questions from different

 listers. One extended thermocouple wires and has a high reading and the

 other is questioning if running thermocouple next to ignition wires causes

 incorrect readings.

 

        Roger

 <winmail.dat>

nuckolls.bob(at)aeroelect
Guest

Posted: Wed Feb 01, 2012 9:25 am Post subject: Thermocouple leads

At 10:25 AM 2/1/2012, you wrote:

 	  Quote: 	
		  



I'm not flying yet, so I have no way of testing.  The tech counselor 

was just speculating that this could be a source of inaccurate readings.


	


   Okay, thanks for getting me back on track! Don't

   worry about your wire routing.

   Bob . . .

tim2542(at)sbcglobal.net
Guest

Posted: Wed Feb 01, 2012 10:22 am Post subject: Thermocouple leads

On 2/1/2012 8:25 AM, Jason Beaver wrote:

 	  Quote: 	
		   



 I'm not flying yet, so I have no way of testing.  The tech counselor was just speculating that this could be a source of inaccurate readings.



 Thanks,



 Jason



 Sent from my iPhone

Even if its off so what?  You don't really care what the temps are, you 
	


want to know the peak and then turn to your own set of beliefs re: LOP 

or ROP operations.

You will be the one to drill the hole in your exhaust and where you put 

it makes a tremendous difference in the actual temp.

CHTs different story of course.

Tim

tperry(at)lvtofly.com
Guest

Posted: Wed Feb 01, 2012 10:59 am Post subject: Thermocouple leads

If it a jpi, I have seen an improper ground cause all to read high.  Make sure your instrument is grounded to the engine and not a ground bus inside.



Tim Perry



On Jan 31, 2012, at 11:33 PM, "Dennis Jones" <djones(at)northboone.net> wrote:



 	  Quote: 	
		   

 

 Both CHT and EGT. They are thermocouple wire. I used the exact same wire as the equipment came with. I silver soldered the new lead extensions as shown by Bob. I do have a multimeter that will test thermocouple wire however I have not used that feature as of yet. The one test I have not attempted is the check of the indication without the engine running. My studies show that they should indicate ambient temperature.

 

 

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p=365354#365354

longg(at)pjm.com
Guest

Posted: Wed Feb 01, 2012 11:25 am Post subject: Thermocouple leads

I'll second that. On the Dynon an improper ground on 1 device/sensor can/will impact the reading on another. I used to have an old Cadillac which when you moved the electric seat the high beams flashed. They called it a feature. 



Glenn



--

nuckolls.bob(at)aeroelect
Guest

Posted: Wed Feb 01, 2012 5:54 pm Post subject: Thermocouple leads

At 01:20 PM 2/1/2012, you wrote:

 	  Quote: 	
		  



I'll second that. On the Dynon an improper ground on 1 device/sensor 

can/will impact the reading on another. I used to have an old 

Cadillac which when you moved the electric seat the high beams 

flashed. They called it a feature.



Glenn


	




    Kudos Tim and Glenn. If the thermocouples are physically

    welded to the bottoms of their thermowells . . . and they

    often are . . . then what ever voltage difference that

    exists between the crankcase and the instrument's ground

    will ride on top of the thermocouple signals as a common

    mode voltage.



    All of thermocouple conditioning chips I've worked with

    for the last 20 years have a considerable tolerance to

    DC common mode interference but if the interference has

    alternator ripple on it, it might be another matter. Hence

    the questions about effects of alternator ON versus OFF.



    It would also be a good experiment to run a temporary

    instrument ground to the crankcase just to see if it

    makes any difference.

   Bob . . .

james(at)etravel.org
Guest

Posted: Thu Feb 02, 2012 2:00 am Post subject: Thermocouple leads

Another "lightbulb" reply, thank you.  I know I've read this in the Connection, but still, a reminder doesn't go amiss. 



Is this effect mitigated by having a common ground on the firewall, with a braided strap to the engine?  If the instruments are grounded to the forest of tabs, and that's only a short distance along a fat piece of copper to the engine... 

 



James



On 1 February 2012 22:22, Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote:

 [quote]--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)>

  



 At 01:20 PM 2/1/2012, you wrote:

  	  Quote: 	
		   --> AeroElectric-List message posted by: <longg(at)pjm.com (longg(at)pjm.com)>

 

 I'll second that. On the Dynon an improper ground on 1 device/sensor can/will impact the reading on another. I used to have an old Cadillac which when you moved the electric seat the high beams flashed. They called it a feature.

  

 Glenn

 	
 

 



    Kudos Tim and Glenn. If the thermocouples are physically

    welded to the bottoms of their thermowells . . . and they

    often are . . . then what ever voltage difference that

    exists between the crankcase and the instrument's ground

    will ride on top of the thermocouple signals as a common

    mode voltage.

 

    All of thermocouple conditioning chips I've worked with

    for the last 20 years have a considerable tolerance to

    DC common mode interference but if the interference has

    alternator ripple on it, it might be another matter. Hence

    the questions about effects of alternator ON versus OFF.

 

    It would also be a good experiment to run a temporary

    instrument ground to the crankcase just to see if it

    makes any difference.

 

 

   Bob . . . 



[b]

ainut(at)knology.net
Guest

Posted: Thu Feb 02, 2012 4:32 pm Post subject: Thermocouple leads

That brings up a q that you might have answered in the original post:

Does each TC have it's own ground connected to it's own gauge?  That is, 

does each thermocouple supply two distinct lines to it's gauge?  You 

cannot use a common ground for each TC and only tie the signal wire to 

the instrument.

David M.

Robert L. Nuckolls, III wrote:

 	  Quote: 	

 <nuckolls.bob(at)aeroelectric.com>

 At 10:57 PM 1/31/2012, you wrote:

> 

> <jason(at)jasonbeaver.com>

>

> Does anyone know if there are any issues in running EGT/CHT 

> thermocouple wires along side the coax ignition leads from a 

> Lightspeed Plasma II ignition (the lines between the ignition box and 

> the coils)?  My tech counselor said this could be a source of 

> inaccuracy in the temperature reading.

    I doubt it very much. The coax is double shielded

    (electro-static coupling ZERO) and the currents

    flowing in the center-conductor (outbound) exactly

    compliment return currents flowing in the shield.

    How much inaccuracy? You said they read high? All

    read high by the same amount? Are your probes isolated

    from engine ground or do they both electrically and

    thermally connect to the engine? Does turning the

    alternator on/off make any difference? Try turning

    EVERYTHING on to make this test. Present the alternator

    with the largest possibible load.

   Bob . . .

-- 

Tell the truth.  Be honest.  Be responsible to and for yourself.

I liked America when it was free and it's people were responsible and had morals.

Every gram of cocaine you buy from elsewhere contributes to an innocent being murdered in Central and South America.  Grow your own or Stop taking it.

ainut(at)knology.net
Guest

Posted: Thu Feb 02, 2012 4:35 pm Post subject: Thermocouple leads

Also, any (new) junction will create an inaccuracy unless you calibrate 

with the total installation.



David M.



Jason Beaver wrote:

 	  Quote: 	
		   



 I'm not flying yet, so I have no way of testing.  The tech counselor was just speculating that this could be a source of inaccurate readings.



 Thanks,



 Jason



 Sent from my iPhone



 On Feb 1, 2012, at 10:04 AM, "ROGER&   JEAN CURTIS"<mrspudandcompany(at)verizon.net>  wrote:



    

>> Does anyone know if there are any issues in running EGT/CHT

>> thermocouple wires along side the coax ignition leads from a

>> Lightspeed Plasma II ignition (the lines between the ignition box

>> and the coils)?  My tech counselor said this could be a source of

>> inaccuracy in the temperature reading.

>>        

>     I doubt it very much. The coax is double shielded

>     (electro-static coupling ZERO) and the currents

>     flowing in the center-conductor (outbound) exactly

>     compliment return currents flowing in the shield.

>

>     How much inaccuracy? You said they read high? All

>     read high by the same amount? Are your probes isolated

>     from engine ground or do they both electrically and

>     thermally connect to the engine? Does turning the

>     alternator on/off make any difference? Try turning

>     EVERYTHING on to make this test. Present the alternator

>     with the largest possibible load.

>

>

>    Bob . . .

>

>         I believe you are combining 2 questions from different

> listers. One extended thermocouple wires and has a high reading and the

> other is questioning if running thermocouple next to ignition wires causes

> incorrect readings.

>

>         Roger

> <winmail.dat>

>      



    


	


-- 

Tell the truth.  Be honest.  Be responsible to and for yourself.



I liked America when it was free and it's people were responsible and had morals.



Every gram of cocaine you buy from elsewhere contributes to an innocent being murdered in Central and South America.  Grow your own or Stop taking it.

nuckolls.bob(at)aeroelect
Guest

Posted: Thu Feb 02, 2012 5:39 pm Post subject: Thermocouple leads

At 06:01 PM 2/2/2012, you wrote:

 	  Quote: 	
		  



Also, any (new) junction will create an inaccuracy unless you 

calibrate with the total installation.



David M.




	


   A set of thermocouple leads can have quite a few

   extraneous junctions without affecting accuracy

   as long as (1) current in the leads is very low

   indeed approaching zero. Such is the case with most

   modern thermocouple instruments using specialized

   integrated circuits for thermocouple signal

   conditioning.  And (2) EACH junction needs to be

   repeated in number and kind on both sides of the

   thermocouple pair.



   This is described in more detail here:



http://aeroelectric.com/articles/excerpt.pdf





   Bob . . .

millner(at)me.com
Guest

Posted: Thu Feb 02, 2012 7:48 pm Post subject: Thermocouple leads

Not exactly grue, David... if it's a chromel/chromel junction and a 

alumel/alumel junction, there's no potential developed across it, so 

nothing to calibrate out.   If, for instance, someone inserts some 

copper wire, you'll have chromel/copper and copper chromel junctions, 

and assuming they're separated, and at different temperatures, that 

temperature difference CANNOT be assumed to be constant... so there's no 

way to calibrate it out.



So... either it doesn't matter, or it can't be known.  No middle ground.



Paul



On 2/2/2012 4:01 PM, David wrote:

 	  Quote: 	
		   



 Also, any (new) junction will create an inaccuracy unless you 

 calibrate with the total installation.



 David M.

millner(at)me.com
Guest

Posted: Thu Feb 02, 2012 7:48 pm Post subject: Thermocouple leads

Hmmm, Bob... the physics doesn't support your assertion, unless you 

(mistakenly I'd think) assume that all those junctions are somehow held 

at the same temperature.  And how would you accomplish that?



With the relatively common high impedance measuring devices, resistance 

in the leads isn't really the issue... but adding uncontrolled junctions 

at different temperatures can sure play havoc with accuracy.



Paul



On 2/2/2012 5:27 PM, Robert L. Nuckolls, III wrote:

 	  Quote: 	
		   A set of thermocouple leads can have quite a few

   extraneous junctions without affecting accuracy

   as long as (1) current in the leads is very low

   indeed approaching zero. Such is the case with most

   modern thermocouple instruments using specialized

   integrated circuits for thermocouple signal

   conditioning.  And (2) EACH junction needs to be

   repeated in number and kind on both sides of the

   thermocouple pair. 


	


-- 

Please note my new email address!

millner(at)me.com

ainut(at)knology.net
Guest

Posted: Thu Feb 02, 2012 8:04 pm Post subject: Thermocouple leads

The OP didn't say whether he was using old style instruments or newer, 

(more digital) ones.

David M.

Robert L. Nuckolls, III wrote:

 	  Quote: 	

 <nuckolls.bob(at)aeroelectric.com>

 At 06:01 PM 2/2/2012, you wrote:

> 

>

> Also, any (new) junction will create an inaccuracy unless you 

> calibrate with the total installation.

>

> David M.

>

   A set of thermocouple leads can have quite a few

   extraneous junctions without affecting accuracy

   as long as (1) current in the leads is very low

   indeed approaching zero. Such is the case with most

   modern thermocouple instruments using specialized

   integrated circuits for thermocouple signal

   conditioning.  And (2) EACH junction needs to be

   repeated in number and kind on both sides of the

   thermocouple pair.

   This is described in more detail here:

 http://aeroelectric.com/articles/excerpt.pdf

   Bob . . .

-- 

Tell the truth.  Be honest.  Be responsible to and for yourself.

I liked America when it was free and it's people were responsible and had morals.

Every gram of cocaine you buy from elsewhere contributes to an innocent being murdered in Central and South America.  Grow your own or Stop taking it.

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