Solder thermocouple?

[Bill]

I got a new extruder to replace my Replicator 2's bad one. Should I cut the thermocouple wires and solder it in, or, use the whole wire and follow it down to wherever it plugs in?

Bill.

[Jeffrey Ballard]

you can not solder it.

Either reuse the old thermocouple, or replace the entire old one wire and all.

On Fri, Jan 11, 2013 at 7:34 PM, Bill <big...@gmail.com> wrote:

I got a new extruder to replace my Replicator 2's bad one.  Should I cut the thermocouple wires and solder it in, or, use the whole wire and follow it down to wherever it plugs in?

Bill.

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[Bill]

I had a feeling that was the deal. Thanks. Now, I just need to follow it back to wherever it goes.

Bill

[Z LeHericy]

thermocouples are not just the sensor at the end, but the entire wire. It is possible to cut and re-weld the wires, but not solder, as that adds an aditional junction between dissimilar metals.

-Zeno LeHericy

//((=:Z:=))\\
INVENTIONS
Technologies
zinventions.com

On Fri, Jan 11, 2013 at 5:11 PM, Bill <big...@gmail.com> wrote:

I had a feeling that was the deal.  Thanks.  Now, I just need to follow it back to wherever it goes.

Bill

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[Doug McNutt]

At 17:41 -0800 1/11/13, Z LeHericy wrote:
>thermocouples are not just the sensor at the end, but the entire wire. It is possible to cut and re-weld the wires, but not solder, as that adds an aditional junction between dissimilar metals.
>
>-Zeno LeHericy
>
>//((=:Z:=))\\
>INVENTIONS
>Technologies

><http://zinventions.com>zinventions.com


If the solder, the third metal, is all at the same temperature as the first millimeter of each of the other wires the voltage output of the thermocouple is the same as without solder.

The real problem is the difficulty of tinning the thermocouple alloys. Ordinary tin-.lead solder won't hack it with any flux known to man. Silver solder with a brazing flux works fairly well but you need a tiny gas-oxygen torch to make it happen.

A tiny crimp sleeve usually works fine but like the third metal above it's made of has the be all at the same temperature.

As for the OP a joint in one of the thermocouple wires in a thermal region that is passing from a high temperature to a voltmeter there WILL be a temperature gradient along the path and a any splicing will introduce an error. That's pretty much why one uses the thermocouple alloys for the whole length in the first place. Where the thermocouple wires are connected to the voltmeter it's important that the two connection points be at the same temperature.
--

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[Jason Preuss]

I just received instructions on how to replace the thermocouple yesterday.

https://groups.google.com/forum/#!topic/makerbot/tAaRdfzMoms