Re: Thermocouple compatible bulkhead connector?

Rick Hole

I was curious about this as in theory the additional dissimilar metal junction will cause errors in the readings. As an experiment I tried connecting a type K thermocouple to a digital thermometer readout with a length of copper wire spliced in. With the thermocouple immersed in a hot oil bath I watched the temperature displayed as I used a hot air gun to heat the junction of copper to thermocouple wire. I thought I could see 1-2 degrees change heating the junction from ambient to as hot as the gun would deliver, but it was difficult to tell the change from random drift.

I have forgotten if I repeated the experiment with a type J thermocouple. The metals involved are different and I would not assume the same results without testing.

So my conclusion is, for type K as used in EGT probes and often used for CHT, you can use the non-thermocouple connector or even use copper extension wire without significant error. And as long as all the cylinder's wires are the same temperature at the change of metal, all the errors are the same magnitude and direction, so with EGTs where only the trend is important, you are doubly ok.

Rick Hole

--- In Q-LIST@..., "John Loram" <johnl@...> wrote:

Thanks for that Sam. Your comment forced me to rethink the problem and I
realized that I had not considered that I was running both sides of each
thermocouple leg through the same connector (duh!), and consequently, the
effect of the dissimilar metals of the connector would be cancelled out so
long as both the male and the female pins of the connector are the same

Cool! thanks again, -john-

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