SNIP
    > Mark,
    >
    > The shielding on millivolt and milliamp wiring is either
   terminated at
    > the device end or the "control" end (reading end) of the circuit but
    > not both OR neither, and it should be connected to the ground bus or
    > terminal(s). The shielding should be "continuous" from probe to your
    > reading device/control device. There is a quick treatise on:
    >
    > http://www.omega.com/prodinfo/Thermocouples.html
    >
    > What size was the hole you drilled (diameter) for the
   thermocouple you
    > inserted? I think that's pretty cool that you made your own by
   welding
    > the bi-metal wiring together. Never heard of anyone doing that.
    >
    > Allen


    > Allen,
    > There is a metal tip that fits into the exhaust header that the
    > shield is attached. I never really thought much about it, but I
    > imagine that provides the ground for the shield (from the exhaust
    > system to the engine block and then to ground).
    >
    > As for welding the ends of the TC wire for the CHT probes, I believe
    > I got that idea from Tracy Crook. I'm not sure he suggested using a
    > TIG welder, but the idea was the same. Worked great (price was
    > right too). So, should the tc leads be shielded?
   --------------------------------------------------------------

   We used to make Thermocouples using a 'Variac", and a pool of
   mercury under oil. Insert a lead from the Variac into the mercury,
   connect the other lead to the twisted together TC wire, and dip it
   through the oil into the mercury. It will arc weld the TC tip, and
   the oil keeps the mercury vapor down. OHSA probably would object now.

   Bill Schertz


   Bill,

   That's very interesting. I'm used to specifying and buying
   thermocouples from instrument vendors. That includes the thermowell.
   That's why I was curious as to the size/diameter of the hole that Mark
   drilled in his block. I was going to see if I could find something that
   would work that was "off the shelf". That would include a thermowell,
   thermocouple and whatever else was needed to install it. I'm not sure
   that the bimetal wiring stuck in the hole would continue to give
   adequate information.

   Allen
   Houston


   Allen, Do you know about omega.com. They have tons of thermal couples.
   http://www.omega.com/toc_asp/sectionSC.asp?section=A&book=temperature
   Wire down to .005 inches in diameter.

   Paul Lamar ...No rotor no motor.
   ------------------------------------------------------------------------------

   Here's a short article which will give you a good overview of TC
   junctions, wire types, etc.

   http://www.picotech.com/applications/thermocouple.html

   I use type K (Chromel/Alumel) wire for most of my home and
   automotive projects.  To make a junction, I twist the wires together
   and give it a good smack with a HAMMER!  It is not as strong as a
   welded junction, but much faster and just as accurate.   I have also
   used an oxy/acetylene torch to form a junction bead.   In college
   (1960), I believe we had some sort of spot welder we could use if we
   were not in a hurry or were using expensive (Platinum/ Rhodium) TC wire.

   For most engine temperature monitoring,  were are interested in
   repeatability of a given  temperature range rather than the actual
   temperature traceable back to the bureau of Standards.

   Joel



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