Matronics Email Lists :: View topic

Matronics Email Lists
Web Forum Interface to the Matronics Email Lists

Get Email Distribution Too! FAQ Search Memberlist Usergroups Register

Profile Log in to check your private messages Log in

EI vs JPI
Goto page Previous 1, 2, 3 Next

Matronics Email Lists Forum Index -> TeamGrumman-List

View previous topic :: View next topic

Author Message

Discover

Joined: 26 Feb 2007
Posts: 429

Posted: Sun Mar 29, 2009 6:46 pm Post subject: EI vs JPI

Yeah I just Read Steve's post again. Steve  didn't use JPI and JPI probers. He used solely EI equipment

  

 His post last year is here:

 http://grumman.net/archive/2008/msg00193.html

  

 I think that the idea that it is the EI fixed  probe that is in error is a new idea recently introduced into this year and a  half long thread. Last year and in Gary's article in the STAR the conclusion was  that the JPI probe did not represent what Lycoming measured.

  

 At this point it is just speculation as to  what type probe was used by Lycoming or perhaps even if they used a  probe.

  

 Like Sgt Friday says lets just say with the  facts... just the facts

  

 [quote]   ---

Discover

Joined: 26 Feb 2007
Posts: 429

Posted: Sun Mar 29, 2009 6:46 pm Post subject: EI vs JPI

Steve's conclusion "the EI longer P-101 probe  does indeed read hotter than the short P-100 probe by about 3.5 degrees  F"

 [quote]   ---

az_gila

Joined: 17 Jun 2006
Posts: 99
Location: Tucson, AZ

Posted: Sun Mar 29, 2009 6:51 pm Post subject: EI vs JPI

Not according to the govt. web site that has specification records back to the 60's



 That's why I put it above speculation....  gil A



 At 07:31 PM 3/29/2009, you wrote:

 [quote] Perhaps there was a milspec probe like the one EI uses today in use on Lycomings certification tests...

  

 Like Isaid earlier we are just speculating

   ---

az_gila

Joined: 17 Jun 2006
Posts: 99
Location: Tucson, AZ

Posted: Sun Mar 29, 2009 6:58 pm Post subject: EI vs JPI

Sorry... I mixed up the vendors...



 I think the "touch the metal probes" (like the Mil-Spec ones) probably read higher.



 However, in agreement with Cliff - there well could be other things in play here when milliVolts are being measured.  



 Grounds and differences in grounds, even along the wire to the instrument, could affect readings.



 That is why I suggest playing around with extra ground wires to see if the differences between the instruments change.  The instrument ground to the engine case would seem to be the first obvious wire to try.



 gil A



 At 07:35 PM 3/29/2009, you wrote:

 [quote] Gil,

  

 You didn't read the post very well. I removed all but the one sentence from the post that you missed. Want to change your belief?

 Ned

  

 ---

pitts_pilot(at)bellsouth.
Guest

Posted: Sun Mar 29, 2009 7:02 pm Post subject: EI vs JPI

Are we really getting anal over 3.5 degrees???  Less than 1% error?

 Linn

 

 923te wrote: [quote]            Steve's conclusion "the EI longer P-101 probe does indeed read hotter than the short P-100 probe by about 3.5 degrees F"

    	  Quote: 	
		       ----- Original Message -----

   	
 [b]

Discover

Joined: 26 Feb 2007
Posts: 429

Posted: Sun Mar 29, 2009 7:04 pm Post subject: EI vs JPI

I'm curious about the wire runs from the  thermocouple to the instrument head. I know that some types like the old Alcor  wires could not be cut. EI and JPI CAN be cut. I'm curious about that and about  the effect for different length and routing under cylinders were the heat is  higher. I think the theory behind teh system is to have one hot source (at the  cylinder head) and one cold source ( at the gauge). I'd like to know more  about the effects of multiple hot and cold sources along the wire

 [quote]   ---

Discover

Joined: 26 Feb 2007
Posts: 429

Posted: Sun Mar 29, 2009 7:04 pm Post subject: EI vs JPI

No Linn, the difference in question is more  like 70 deg F

 [quote]   ---

az_gila

Joined: 17 Jun 2006
Posts: 99
Location: Tucson, AZ

Posted: Sun Mar 29, 2009 7:13 pm Post subject: EI vs JPI

Ned... try this for a starter...  gil A



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



 

 At 08:06 PM 3/29/2009, you wrote:

 [quote] I'm curious about the wire runs from the thermocouple to the instrument head. I know that some types like the old Alcor wires could not be cut. EI and JPI CAN be cut. I'm curious about that and about the effect for different length and routing under cylinders were the heat is higher. I think the theory behind teh system is to have one hot source (at the cylinder head) and one cold source ( at the gauge). I'd like to know more about the effects of multiple hot and cold sources along the wire

   ---

Discover

Joined: 26 Feb 2007
Posts: 429

Posted: Sun Mar 29, 2009 7:20 pm Post subject: EI vs JPI

I'm a big fan of Bob Knuckolls. We even had  him speak at our Pulsar builders convention. I've read this before but I'll read  it again. A brief scan seems to indicate no address of my questions  tho...

  

 I have these questions because I know how Gary  has routed his wires. Very nice hidden installation but it always mae me wonder  if the under cylinder heat may have an affect

 [quote]   ---

az_gila

Joined: 17 Jun 2006
Posts: 99
Location: Tucson, AZ

Posted: Sun Mar 29, 2009 7:27 pm Post subject: EI vs JPI

The GEM also allows for cutting of the wire leads.



 This is probably due to modern electronics using FET transistor input devices with very high input resistances.



 The older specifications made a big deal of the thermocouple resistance, which makes me think that the older Alcor instruments were affected by total resistance in the leads with a completely different input circuit.



 This bit is definite, but informed, speculation...:^)



 Some more far out speculation - the lead connections could have changed over the last period of a few years due to the removal of lead from solder by EU and Japanese regulations - the RoHS Directive.

 Manufacturers have changed the plating composition on connectors that may come into play at the probe to lead wire connections.  In lots of commercial cases (and a few Mil-Spec cases, unfortunately) these changes have NOT been reflected in part number changes.



 gil A



 At 08:06 PM 3/29/2009, you wrote:

 [quote] I'm curious about the wire runs from the thermocouple to the instrument head. I know that some types like the old Alcor wires could not be cut. EI and JPI CAN be cut. I'm curious about that and about the effect for different length and routing under cylinders were the heat is higher. I think the theory behind teh system is to have one hot source (at the cylinder head) and one cold source ( at the gauge). I'd like to know more about the effects of multiple hot and cold sources along the wire

   ---

az_gila

Joined: 17 Jun 2006
Posts: 99
Location: Tucson, AZ

Posted: Sun Mar 29, 2009 7:32 pm Post subject: EI vs JPI

At 08:22 PM 3/29/2009, you wrote:

  	  Quote: 	
		   I'm a big fan of Bob Knuckolls. We even had him speak at our Pulsar builders convention. I've read this before but I'll read it again. A brief scan seems to indicate no address of my questions tho...

  

 I have these questions because I know how Gary has routed his wires. Very nice hidden installation but it always mae me wonder if the under cylinder heat may have an affect 	




 The critical portion would be not the leads themselves but the probe/lead connection, which is only a short distance from the probes, and in the hot area by your description above.   gil A    [quote][b]

Discover

Joined: 26 Feb 2007
Posts: 429

Posted: Sun Mar 29, 2009 7:36 pm Post subject: EI vs JPI

Interesting Gil,

  

 we know that temperature affects resistance.  Also, Length of wire is a concern. for example, if you cut the thermocouple  wires and make them different lengths from the heat source to the cold source so  that some stay hotter than others and resistance is not constant what  effect would that have on the algorithm that puts the numbers on the the  gauge?

 [quote]   ---

az_gila

Joined: 17 Jun 2006
Posts: 99
Location: Tucson, AZ

Posted: Sun Mar 29, 2009 8:06 pm Post subject: EI vs JPI

Ned... more stuff.



 Excellent description - with pics - of grounded vs. ungrounded - interesting that grounded are faster respnse, but ungrounded are better in electrically noisy environments



  http://www.omega.com/custom/faq.html#9



 Interesting comments on wire length and high impedance sensors here



  http://www.omega.com/prodinfo/ThermocoupleWire.html



 A good detailed reference - I need to absorb this one...



  http://www.omega.com/temperature/Z/pdf/z021-032.pdf



 more



  http://www.omega.com/techref/thermoref.html



 As you might guess, Omega is a premier US source of thermocouples....:^)



 A bit more basic one here...



  http://www.status.co.uk/data/handbook_sections_1_to_4.pdf



 Enough here to guarantee you will fall asleep quickly...:^)      gil A



 [quote] I'm a big fan of Bob Knuckolls. We even had him speak at our Pulsar builders convention. I've read this before but I'll read it again. A brief scan seems to indicate no address of my questions tho...

  

 I have these questions because I know how Gary has routed his wires. Very nice hidden installation but it always mae me wonder if the under cylinder heat may have an affect

   ---

Discover

Joined: 26 Feb 2007
Posts: 429

Posted: Sun Mar 29, 2009 8:22 pm Post subject: EI vs JPI

Thanks Gil.

  

 I was chasing rabbits whilst looking for some  references. have most of the Omega books...guess I should dust them off...noooo  it's just easier to use the net;)

  

 The rabbit...Interesting article on the  history of temp / heat measurement

 http://www.springerlink.com/content/r1n5773kug453405/fulltext.pdf

  

 Actually got me to chase a rabbit to colditz  Where there is a clay called the colditz clay that was used to make the  secret formulae, at the time, porcelain.

 Back in the 1700's the king of Saxonia  (east germany) evidently had teh European market on this typr of  porclain...

  

 I keyed in on colditz because of its'  significance during WWI and WWII as  using their castle as a prisoner  of war camp...the unescapable prison where during WWII the prisoners were  constructing a GLIDER to launch from the top of the castle, thus the birdmen of  colditz movie

  

 Isn't this forum great! no nanny to kick me  off!

  

 [quote]   ---

flyv35b(at)minetfiber.com
Guest

Posted: Mon Mar 30, 2009 5:49 am Post subject: EI vs JPI

This has been my point, there is very little  difference between the two types of probes.  If I recall this data from  Steve was obtained on different flights so the 3.5F is probably within the  margin of error.  We don't have all the data or evidence yet and the jury  is still out.

  

 Cliff

 [quote]   ---

airman(at)appledumplings.
Guest

Posted: Mon Mar 30, 2009 6:21 am Post subject: EI vs JPI

#1  you guys really need to learn how to cut the uneeded part of the

original message when you reply. It takes 10 seconds. I know at least one

of you guys is stubborn because of old GG issues. But man I have tried to

read this forum for some time and it is quite annoying. But on a day like

today where many do it .. it is not just annoying it is unbearable and

unreadable.



With that said. I recently installed a JPI EDM 700  I previously had an

alcor EGT only.  I am seeing 450 on the back cylinders and

380-400 on the front sometimes in cruise if I lean

aggresively.(I have not seen it get higher in climb) Even with keeping it

a bit rich I run 430 on the back.



My history. Atlanta,Ga AA5b 1976 10 years 450 SMOH. Good compressions

all 74 or higher last 3 annuals with one exception of a 72. Had high oil

temps(1-2 needle widths below redline in summer) and put new baffle seal

and sealed some seams in the side baffles. I still

wonder about the baffle sheets on the bottom. It doesnt fit well next to

the case in the back bottom. Anyway we checked the gauge and vernatherm

and I gave up and got a bigger cooler. Which helped, now 200-210.

After all this I put in the JPI and get the above temps. I have not gone

back and had someone check to see if the ground was installed correctly. I

will do this soon.  My current A&P also made a comment about the JPI.

Saying he has had a few people install them and get so distraught that

they seel theri airplanes or do overhaul early. He seems less concerned.

And he has looked for any overheat indicators.

I personly have been running it a bit rich because until I am assured it

is instrumentation It  just makes me nervous.



Thomas

flyv35b(at)minetfiber.com
Guest

Posted: Mon Mar 30, 2009 6:48 am Post subject: EI vs JPI

 	  Quote: 	
		   #1  you guys really need to learn how to cut the uneeded part of the

 original message when you reply.


	


You are so right.  I do it on the GG but have been guilty of not doing it 

here.



Cliff 

-- 

We are a community of 6 million users fighting spam.



The Professional version does not have this message

GrummanDude

Joined: 15 Jan 2006
Posts: 926
Location: Auburn, CA

Posted: Mon Mar 30, 2009 9:27 am Post subject: EI vs JPI

 	  Quote: 	
		   Maybe you guys need to ask Steve Peach about the two  different styles of EI probes, bayonet and standard P-100, that he tested and  found very little difference between the two.  The large differences in  temperature mentioned are between JPI with the bayonet and EI with the fixed  probe.  And all the accusations, or implications at least, are that the  fixed EI probe does not measure the true temperature.  There is a real  possibility that it could be due to something completely  different.

    

   Cliff

 	
 Finally, Cliff, you hit the nail on the head.  I agree.  There is a real possibility there is something going on that could account for the differences in temperatures.  I doubt, seriously, that it is just the probes.

  

 

  And.  It has nothing to do with a recent change in vendors.  I first noticed this difference around 1995 when I installed my first JPI 700.  

  

 

  And.  It isn't just my plane.  I installed a JPI 700 in one Comanche and a JPI 800 in another Comanche in place of previously installed EI units.  Both owners came back saying their engines were running hot.  One owner, the 700, bought another EI and had me put it in instead.  The other owner was willing to accept th e higher readings.

  

 

  Gil.  Just how many grounds is enough?  Are you concerned about ground loops?  I've run the ground to a common avionics ground AND to the ground on the engine from the avionics ground.  No change.  I've tried just the avionics ground.  I've tried just the engine ground.  No change.  

  

 

  Like I wrote in the STAR, the temps start out the same before start-up.  The JPI temps rise faster and to a higher reading than the EI temps.

  

 

  And.  There is no way to know the actual test set up used by Lycoming.  

  

 

  I have an old Gem in a box somewhere.  It has no digital readout.  Gil, if yours has no digital readout, with 25 degree per bar accuracy, how do you know what the temperature is?  

  

 

  And. Speculation:  I would expect that the makers of these analyzers took into consideration various millivolt differences.  If they saw differences of 3 degrees, I doubt they cared.

  

 

  And.  If this had only happened to one installation, then I would look at the installation.  It is a universal experience that the JPI reads higher.  

  

 

 

 

 --

_________________
Gary
AuCountry Aviation
Home of Team Grumman

GrummanDude

Joined: 15 Jan 2006
Posts: 926
Location: Auburn, CA

Posted: Mon Mar 30, 2009 9:46 am Post subject: EI vs JPI

Just to add to the mix.   

 

  On the flight tests, we also measured Oil Temp and OAT with the EI.  Oil temp was measured at the oil filter adaptor and OAT was a probe stuck out the canopy at the top.   

 

  Oil temp on the EI was within 5 degrees of the oil temp measured by the JPI in the front right galley plug.

  

 

  Oat on the JPI was slightly colder, 1 to 4 degrees, with the JPI probed located under the left wing at the most forward inspection cover.

 

 

 --

_________________
Gary
AuCountry Aviation
Home of Team Grumman

GrummanDude

Joined: 15 Jan 2006
Posts: 926
Location: Auburn, CA

Posted: Mon Mar 30, 2009 10:32 am Post subject: EI vs JPI

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

 

  

 

   ------------------------------------------------

  It sounds to me like this describes the basic EI circuit.  I know you can't change the length of the leads (on the unit I used).  The reference temperature is the back of the unit?  Not sure if I would rely on that.

  

 

 

  Except for a few cautions, the unpowered thermocouple gage

   is quite attractive. It can be accurate and requires no wiring to

   ship's DC power. Such an instrument is illustrated in View

   -C-. Obviously, the reference-junction for this instrument

   exists right where the thermocouple wires bolt to the back of

   the instrument. Reference-junction compensation doesn't have

   to look like a 0oC ice bath. The reference-junction compensator

   just needs to know what the temperature is at the studs on the

   back of the instrument case; no problem since the

   compensation circuitry is right inside the case!

 

   ------------------------------------------------

  This sounds more like a JPI unit.

  

 

 

   While on the topic of high impedance instruments for

   thermocouples, I'll call your attention to Figure 14-12.

   In View -A- the hot-junction and reference-junction

   setup is similar to Figure 14-10, View -A- except: an

   electronic amplifier inserted between thermocouple

   wires and indicator. Some interesting things happen

   when you add an amplifie r. (1) the indicator becomes a

   simple, much less expensive, voltmeter and (2) the

   current flowing in the thermocouple wires is for all

   practical purposes, zero. Length of thermocouple wire

   is no longer critical; insertion of a selector switch to

   manage many thermocouples is feasible. The last

   inconvenience to eliminate is the requirement for an ice

   bath . . . .

 

  

 

   ------------------------------------------------

  This sounds like what was done on the AG5B.  No wonder their temp gauges are so bazaar. 

  I try to avoid

 

 

    bringing a thermocouple through any kind of connector

   along with other wires. There's a lot of temptation on the

   part of builders to bring all wires penetrating a firewall

   through on some kind of connector. For cost, weight

   and time savings, I recommend fabricating firewall

   penetrations from ordinary grommets with sheet metal

   fire shields.

 

  

 

  ------------------------------------------------

 

  Figure 14-3:  A:  JPI installation.    B: EI Installation

   ------------------------------------------------

 

  

 

  http://www.status.co.uk/data/handbook_sections_1_to_4.pdf

 

  

 

 

   Thermocouples with grounded junctions display response times some 20 to 30%

   faster than those with insulated junctions. Very good sensitivity is provided by fine

   gauge unsheathed thermocouples. Wit h conductor diameter in the range 0.025mm

   to 0.81mm, response times in the region of 0.05 to 0.40 seconds can be realised.

 

  

 

  

 

  

 

  

 --

_________________
Gary
AuCountry Aviation
Home of Team Grumman

Display posts from previous:

	Matronics Email Lists Forum Index -> TeamGrumman-List	All times are GMT - 8 Hours Goto page Previous 1, 2, 3 Next
Page 2 of 3

Jump to:

You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum