welding thin wire/leads

[slim pickens]

At work, we use a small spot welder to attach EPD and thermocouple leads to test specimens. The weld produced is basically a spot weld to melt the first few thousandths of wire onto the specimen surface. The wire gages are super thin - think angel hair for some of the platinum T/C wires. The "lab grade" spot welder is on the fritz, works about 50% of the time. Replacement cost is ~$10K. Is there a way to use a power resistor (or similar device, either shop made or OEM) to get the amps from a typical TIG welder from 5 down to 0.5 or less? I was thinking of modifying the spot weld leads for use with a small TIG. Is this feasable? Is there a 'turn key' device to get the amps down to near nothing? Would it even be able to get an arc started that low?

 

[Jon Bohlander]

Not really what you asked for but heres a link to a microwelding association. I'm definetly not a precision welder but have seen the type of work that is possible by a skilled welder and a micro-TIG machine as far as mold repairs. These guys weld with a microscope and amaze me. So maybe a micro-TIG is the answer.

I have to ask why do you have to weld the T/C to the specimen? More accurate readings?

http://www.usmwa.com/home.htm

 

[slim pickens]

The T/C leads generally give better results when spot welded to a metallic surface as it has better surface contact (measuring surface temp vs surrounding air temp in hot furnace/cold chamber). The EPD leads have to be welded to get good contact, not much other way to do it.

 

[snowman]

Slim,

Have you tried any of the adhesive backed thermocouples that Omega sells?

I used them for quite a while and they seemed to work quite well. I used them from -40 C to 100 C

-Jacob