Comments on: Measuring Temperature: Thermocouples Made Easy and Cheap

By: Dave A

Dave A — Sat, 26 Dec 2009 16:46:49 +0000

Hey Beebe,
How did it work?

By: beebe

beebe — Thu, 24 Dec 2009 23:49:19 +0000

Ok, I’ve looked into welding thermocouple wires a little more and I think a capacitive discharge welder can be made on the relative-cheap for those without welding equipment using parts available from Radio Shack. A high-current NPN transistor, ~2200 uF 30v cap (?), battery charger, and a push button switch would probably be the entire parts list. I’ll test and report back. I’m not sure shielding gas is needed for these hobby-grade junctions.

As an aside, I found that my TIG setup welds wire nicely. I set the current to the lowest setting, high frequency off, and DC Reverse polarity. I’ll be testing these junctions tomorrow on my Christmas ribeye roast!

By: Dave A

Dave A — Wed, 02 Dec 2009 02:14:15 +0000

Nice! We don’t have a real mig at the school (FCAW only) so I can’t reproduce. Anyone with a real Mig take note.

By: beebe

beebe — Tue, 01 Dec 2009 19:28:54 +0000

I like the article!

I had good luck welding small therocouples with the following MIG method:

1. Sharpen a short piece of 1/16″ TIG tungsten (Pure Tungsten)

2. Drill out the MIG tip to 1/16″ and tap and drill for a set screw (I used 6-32) to hold the tungsten in the MIG tip.

3. Bend thin aluminum sheet to make “tweezers” out of aluminum to pinch the thermocouple wire in a vice. The melted thermocouple wire won’t stick to the aluminum.

4. Strip thermocouple wire and twist the two together and clamp it in the aluminum tweezers with the twisted part sticking out.

5. Clamp the MIG ground clamp to the vice/aluminum tweezers.

6. With all wire removed from the MIG gun, pull the trigger to activate the shielding gas (I set up with pure Argon) and touch the sharpened tungsten tip to the twisted wire sticking out of the “tweezers”.

7. The arc will melt the wire sticking out down into a tiny ball. Adjust the protruding length of wire to get the right ball size. The shielding gas will keep the wire from oxidizing as it melts.