Multiple receivers on one thermocouple

[MiniMopar]

OK, I have boned-up on thermocouple theory and I think this will work, but I wanted to talk through it to see if I am missing something. I have an EGT guage and currently a single K-type thermocouple. I also have the TechEdge 2A0. My goal is to be able to observe the EGTs on the guage, but also to be able to log them with the 2A0.

Now, each time you join two dissimilar metals together, you get a thermocouple. In order to know what the temperature of the probe's thermocouple is, you have to make sure that you don't introduce any others that you can't track the temperature of through some other means. The one you can't avoid is the one at the guage. The guage itself will measure the temperature there and compensate for that junction. The theory also states that you can go from metal A to metal B back to metal A. If the temperature of those two junctions is the same, you can disregard those junctions as they cancel each other out.

Now, the cable for my EGT probe just has bare leads and is way too long, so I will just cut it. Now, if I took this extra cable and also connected it in parallel at the same junction on the back of the guage and ran it to the 2A0, the voltage that the 2A0 sees should be unmolested (assuming the guage doesn't load the voltage in some weird way or vice versa).

Am I correct?

[BadAssPerformance]

Sounds like it is worth a try for sure

[csxtra]

Russ,

You are correct. As long as you are using real thermocouple wire and keeping the like metals together, it should work fine.

I'm trying to track down a ground loop problem on my EGT datalogging, and I did this exact thing, running it in parallel to determine where the problem lies.

The gauge that doesn't have any reference to ground reads correctly at ambient temps and the #s are reasonable under different engine conditions. And, if I unplug the second connection (to the datalogger), the reading doesn't change.

Hope this helps,

Warren

[Speedeuphoria]

great info!
anyone else have input?
At this point I need a guage source and datalog as well and would like to only use 1 probe if I can get away w/ it

[MiniMopar]

Cool...glad to hear some real world feedback. I was prototyping a circuit to tap into the corrected output from the guage (2-6V, used to drive the guage needle actuator) and transfer that to one of the analog inputs. It would be nicer to let the 2A0 do it's own correction, plus it's simpler since I don't have to map the voltage to the EGT manually afterwards.

[WVRampage]

as long as you dont short it to ground or to the other teminal it should be fine since realy all it does is make power.