Wow!  I lot of response to my question.  This is great!

The VDO gauge that I am using uses a thermocouple, so says the installation
guide.  The resistance of it is under zero ohms.  The length of the cable
that came with the kit is 12' and the additional cable that I bought is 14'
Measuring resistance on the red wire, it is 1.2ohm and the yellow wire is
3.2ohm.

The thermocouple end of the 12' that came with the VDO gauge is simply some
inexpensive looking 18-22 ga 'eye' connectors crimped on the end of the
wires.  Each wire is offset by about 1" so they can not touch each other.
The VDO gauge end of this cable is just the two wires terminating into the
'open air'.  As in you have to crimp on your own female spade connectors to
this end.  To attach the cable to the thermocouple they supply some small
(M2ish) screws with nylock nuts to fasten the coupler to the cable.  The
cable looks a lot like the cable you see used between a household furnace
and the thermostat - i.e. nothing fancy other than a tough outer skin.

David Marshall

Fast Forward Automotive Inc.
4356 Quesnel-Hixon Road
Quesnel BC Canada  V2J 6Z3

http://www.fastforward.ca    mailto:sales@fastforward.ca
Phone: (250) 992 7775        FAX: (250) 992 1160

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Due to the large volume of email  we  receive,  PLEASE  include  previous
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in one message and will result in quicker and more  accurate  responses.

-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com]On Behalf
Of Keith Hughes
Sent: December 28, 2003 9:43 PM
To: vanagon@GERRY.VANAGON.COM
Subject: What makes a pyrometer's cable so special?

Well David, it depends;

If it's a thermocouple, then you need to use thermocouple
extension wire (of the same type, "T", "J", "K", "R", "S", etc.)
and of sufficient gauge to minimize the resistance. The affect of
a few feet of, say, 16-18ga extension wire is negligible on the
calibration. However, if you use regular copper wire, then you're
creating a secondary thermoelectric junction. The thermoelectric
potential generated would then result from the temperature
differential between the TC tip and the connection point to the
extension wire - *not* between the "meter" (where the zero
junction compensation is measured) and the tip. The resulting
error is the difference between the ambient temperature at the
meter, and that at the connection to the extension cable (plus
some minor thermoelectric offset caused by the additional junction
at the meter terminals).