EGT Extension wires

[scottessex]

I need to extend my wires on a type K thermocouple,
Does it need to be special wire? I am having trouble finding out any info.

[edypaul]

Scott
They sell extension wires at Aircraft Spruce and some of the other suppliers.

[GrantR]

Scott,

On my airplane telephone wire was used and it worked fine. Others have told me that works just fine. I tried a different type wire and the results were the same. CHT and EGT were run through the smae phone wire.

[Mike Stone]

Along the same lines...
I have been curious if all that extra braided wiring that comes with these devices needs to remain i.e. it seems certain installations leave this excess wiring wrapped up in a bundle.

[scottessex]

I have plenty of 22 ga wire to extend them,

[Al_Hammer]

The main thing to keep in mind is that thermocouple wire has a certain resistance per foot.
If you shorten the length, the gauge will no longer be matched to the new resistance, so don't do it.

As far as using copper extension wire, here is what it says on Stratomaster's site:

Extending leads of probes and senders
Thermocouple leads as used with the EGT and CHT probes can be extended either with
ordinary copper cable or with special K-Type extension cable. The choice of either depends
on your desired accuracy.
If it is possible in your installation to ensure that both ends of a copper extension cable will be
at the same temperature (or very close), then it is quite possible to use the copper cable. In
most open-air installations this will be the case.
Should this not be possible or you require best possible accuracy at all times, you can obtain
a special K-type extension cable. This cable is made from the same metals as your probes
cable but uses ordinary plastic sleeving to save costs.
In either case, ensure that the cable is not routed close to sources of electromagnetic
interference of any kind. The voltages present in this cable are very small and are subject to
changes applied by external fields. This can lead to false temperature indications.
You can check your installation by using a hand-held transmitter, such as an airband radio. If
you transmit a signal, no change in temperature reading should occur.

The resistance per foot of copper wire is so low that a few feet of extension wire does not change the reading, assuming that the copper wire itself is all at the same temp.

[scottessex]

Thanks Al, that is what I Thought, I know you are not supposed to shorten them.
I need about 3 feet longer, and I remeber when I hooked up a E.I.S. system for a
friend, they did not specify any certain wire, or length for the EGT/CHT section of the wiring.

[Al_Hammer]

Scott, the difference, I think, is that the EIS is not using the thermocouple as a power source to drive a meter. It does not load the thermocouple and therefore it does not matter what the resistance is. The "seebeck" voltage only depends on the temperature difference, so as long as no current flows to cause a voltage drop, you can ignore the cable length.
This is my understanding, sketchy as it is.

[scottessex]

I called the MFG (http://www.exhaustgas.com/Default.asp?RepID=&DepartmentID=&CategoryID=&BasketID=)
And they said it has to be a wire made from the same material as the K type probes,
( a chrome alloy and an aluminum
alloy called chromel-alumel.)
This is for a digital gauge, they can hook me up for abou $18. :)

[Dirtydog]

scottessex :
Sounds better than 30.00 for the factory! They said as long as it was a K type probe.