John Loram <johnl@...>
Given that the pins in a connector are in such intimate contact, I'd be
surprised to learn that there's even one degree of temperature difference
between the junctions; less than the resolution of the measuring system.
It's my impression that all the modern electronic engine monitors
incorporate cold junction compensation within the instrument; it's done with
a thermistor and a few lines of code.
From: Q-LIST@yahoogroups.com [mailto:Q-LIST@yahoogroups.com] On Behalf Of
Sent: Thursday, February 04, 2010 5:07 PM
Subject: [Q-LIST] Re: Thermocouple compatible bulkhead connector?
Yes, but note that in a firewall connector you will expect a higher
temperature on the engine side compared to the cabin side. There will be an
error but it really is not significant. Even if you use the bulkhead
connector as the point where you convert the thermocouple metal wires into
copper (and you will do this somewhere, at least at the instrument) and
error will ocurr. If high accuracy is required, a second thermocouple is
placed at the junction to copper for "cold junction" compensation. But we do
not require that level of precision. EGTs are relative, and CHTs, well, if I
am operating say 5 degrees from red line I will already have taken action.
--- In Q-LIST@yahoogroups. <mailto:Q-LIST%40yahoogroups.com> com, "John
Loram" <johnl@...> wrote:
so, if the two junctions are at the same temperature (as they would besince
they are plugged into one another) they electrically balance out oneanother
and will have no effect on the temperature measurement.[mailto:Q-LIST@yahoogroups. <mailto:Q-LIST%40yahoogroups.com> com] On Behalf
the junction of copper to thermocouple wire. I thought I could see 1-2would
deliver, but it was difficult to tell the change from random drift.extension
wire without significant error. And as long as all the cylinder's wiresare
the same temperature at the change of metal, all the errors are the sameyou
are doubly ok.the
soeffect of the dissimilar metals of the connector would be cancelled out
long as both the male and the female pins of the connector are the same