Thermocouple input thread

[Drake]

I see that the new cable comes with an input for a K type thermocuple. I've never delt with thermocouples, except for the theory of their operation. Do they come in different voltage output ranges for different temperature ranges?

Hows about a little discussion of their variations and use. I'm trying to come up with some good uses, especally for a turbo setup.

[Blacky]

Some info to start the thread

EFILive records temperature in the range 0 to 1024 degrees C at 0.25 degrees C accuracy (EFILive displays it as either C or F).

We added CJC (Cold Junction Compensation) to FlashScan using a dedicated IC. The FlashScan firmware communicates with the CJC IC to obtain the corrected temperature before inserting it into the logged data stream.

More info here:
http://www.brainyencyclopedia.com/encyclopedia/t/th/thermocouple.html

Relevant quote from the above link:

Unfortunately it is not possible to simply connect up a voltmeter to the thermocouple to measure this voltage, because the connection of the voltmeter leads will make a second, undesired thermocouple junction. To make accurate measurements, this must be compensated for by using a technique known as cold junction compensation (CJC). In case you are wondering why connecting a voltmeter to a thermocouple does not make several additional thermocouple junctions (leads connecting to the thermocouple, leads to the meter, inside the meter etc), the law of intermediate metals states that a third metal, inserted between the two dissimilar metals of a thermocouple junction will have no effect provided that the two junctions are at the same temperature.

[GMPX]

I'm trying to come up with some good uses, especally for a turbo setup.

Turbo setups were exactly what we had in mind, alot of guys like to measure the exhaust temp of the turbo's, or the temp after an intercooler.
Look to get an decent EGT from the aero industry, they are widely used on piston planes.
Alot of dyno's have Thermocouple sensors as well, they are handy for measuring under hood temps, intake temps, etc.
Not that we have provision for 8 thermocouples but alot of the big end drag racers run 8 so they can picky lazy or lean cylinders.
Simply put you can't measure 0 - 1024degC using the air intake temp sensor GM provide :-).

I just did a Google on 'Exhaust Thermocouple' and found plenty of places selling what you need, automotive, marine etc....just an example -
http://www.racerpartswholesale.com/stewarn27a.htm

Also of interest (even though it's for a rattler)
http://www.portadiesel.com/docs/egt.html

Cheers,
Ross

[SS2win]

I've been searching around and got a recommendation to check out omega.com. Think that THIS (http://www.omega.com/ppt/pptsc.asp?ref=CF-000_CF-090&nav=) is the ticket. Can anyone confirm?

Also I was told that my Incon manifolds have metric bosses but I can't find a compression fitting that isn't Imperial (NPT). I havent got out there with a wrench yet.. anyone have a guess to what size might it be?

[Patches]

Hey Ross,

Just thought I'd point out that the Stewart-Warner thermocouples you linked to are the type I have that we're still trying to sort out. Specifically, model # STW114653.

http://www.racerpartswholesale.com/stewarn27a.htm

Ed

[Blacky]

Hey Ross,

Just thought I'd point out that the Stewart-Warner thermocouples you linked to are the type I have that we're still trying to sort out. Specifically, model # STW114653.

http://www.racerpartswholesale.com/stewarn27a.htm

Ed

Hi Ed,
Did you get my email last week? This is what I sent:


I have finally go my hands on the same thermocouple that I believe you are using
The label on the box says:
114653 Kit,
Thermocouple
Street W/Harness
Stewart Warner Performance

I hooked the red wire to FlashScan's Alumel (-ve) terminal (Pin A).
I hooked the yellow wire to FlashScan's Chromel (+ve) terminal (Pin B).
See image attached for pinouts.

I tried it connected directly the the short (8 inch) red and yellow wires - that worked ok.
I tried it with the red/yellow (in brown cover) extension wires and that also worked ok.

I measured iced water at 9 Deg C and a naked flame at 405 Deg C.

Did you ever get a different k-type thermocouple to work with FlashScan?
If a different k-type does not work with FlashScan then it may be a faulty FlashScan unit.
If a different k-type does work with FlashScan, then it may be a faulty Stewart-Warner thermocouple.


Regards
Paul

[Patches]

No, Paul. Sorry to say I did not get your emial. Perhaps it went to my old address. My current email is edbon@adelphia.net.

I am happy to hear it worked on your's because it means there's hope for mine. I tried a standard, full-length type-K thermocouple I bought from McMaster-Carr when my Stewart Warner setup wouldn't work and the MacMaster-Carr tc worked perfectly when hooked to the FlashScan module. My S-W thermocouple also works perfectly when directly hooked to the S-W gauge as well - it's only when connected to the FlashScan module that it produces no output. I am now wondering if the orange connector that I attach to the proximal tc wire isn't bad because every other component works when tested separately. But that still doesn't explain why the McMaster-Carr tc did work when connected to the Flashscan unit using the same orange connector. Incidentally I tried the S-W tc wires connected in both positions in the connector.

I think ordering a new connector from you might be the next step to try.

Thanks for the follow-up, Paul. You and Ross have been very helpful in getting this solved.

Ed

[SS2win]

what part numnber did you get from mcmaster? I looked and none of them seemed to fit the bill.

[Patches]

SS2win, I just bought a cheap K-type to test the Flashscan module to make sure it was accepting a signal at that input. The tc I bought would not survive very long installed in the header. I hooked it up to the flashscan module inside the car and used a lighter to heat the tip and verify on my laptop that the Flashscan module was recording the temp change. It worked fine for that test.

The tc mounted in my collecter is the Stewart-Warner one Ross linked to above. There are some pictures of the installation on my web site.

http://redshift.homestead.com/WBO2.html

[Blacky]

I think ordering a new connector from you might be the next step to try.
Ed

We don't carry/stock/sell the thermocouples. The one I have was ordered from the US (by Jesse aka wait4me - thanks Jesse) and shipped out here especially to test for the issues you are having.

Regards
Paul

[GMPX]

But you will fit it to your car now won't you when that new exhaust arrives :lol:

Cheers,
Ross

[Patches]

Paul, I meant the orange 2-terminal tc terminals you sell to hook up to the tc wires.

http://www.efilive.com/forum/download.php?id=421

Only thing is, they are $3.50 but cost almost $20 to ship here. Hmmm . . . suddenly I see a need for a Plan B. :lol:

[Blacky]

You may be able to source those parts locally.

http://www.efilive.com/forum/viewtopic.php?t=1884

Regards
Paul

[SS2win]

http://www.digikey.com has them

1597360000-ND | CONN PCB 3.5MM 20POS SN OR | $1.20
1597370000-ND | CONN PCB 3.5MM 3POS SN OR | $1.86


BTW: Does anyone know if there is a metric pipe thread and what size might be close to 1/8 NPT? Still havent pulled a plug on my incon manifold and put a thread gauge to em...

[Patches]

Thanks guys! :D