Re: [MV] 24 volt pyrometer?

From: jonathon (jemery@execpc.com)
Date: Thu Sep 26 2002 - 07:22:05 PDT


>The thermocouple tip must be of highest quality. A bad thermocouple may get
>its tip burned off and destroy your turbo.

A little thought on probes..... When I installed one on mine I was told by
local LD expert to put in an exposed junction type of probe. This is not
standard for any of the gage companies but can readily be gotten from Omega
for example. This is what you might concider a low quality tip as it will
not last long and you would not want to leave it in very long. The point is
though that the mass is very low compared to a normal probe so you can see
changes in EGT very quickly. I did this and drove it around for a few days
and reported my findings along with boost pressure then I removed it and put
in a normal probe.

A little note about thermocouples (used to design meters for them). If you
need to extend the lead between the probe and the meter, you can use normal
wire, it will work, but it is not proper. The two wires in the cord are
dissimilar metals, for a "K" type they are called Chromel and Alumel (if I
recall proper spelling). Remember that every single point where the metals
change is called a "junction" and it will generate a voltage depending on
what the dissimilar metals are and the temperature difference. If you use
some copper wire to extend the lead then you've added 4 more dissimilar
junctions, normally you only want two, one in the probe and one (ideally) in
the meter. If any one junction has it's temperaure different than the
others it will show up as a change in displayed temperature. So in a nut
shell, don't play around with it, if your investing all this money in probe
and meter then pop for the special thermocouple extenstion cords if you need
one..

>There is a plugged tapped hole in
>it, so that should be easy to fit with some copper tubing and a fitting.

Nylon or polyurethane type plastic tubing works well also, at least mine is
till in going strong after two years.

later,

je



This archive was generated by hypermail 2.1.4 : Wed Apr 23 2003 - 13:21:25 PDT