Temperature Measurement inside the ID of tube during EB weld

[65CCJ]

I'm looking for advise on how I can take a temperature measurement inside the ID near a circuit header board on a pressure sensor. The EB Weld machine makes it difficult to see anything and it done in a sealed vacuum.

Here are the specifics and a pic showing where I want to get a measurement,
Material: 17-4 H1150
OD weld .870"
Weld thickness: .060"
Wall thickness .065"

Is there a thermocouple that can be mounted onto board that is small enough to fit in what is pictured?

Thanks,

War Man

 

[MikeHalloran]

The beam itself is damn hot, and smaller than all the thermocouples I know of, so I'm not sure what you'd actually be measuring.

I suppose you could embed a t/c in the circuit board, and have the circuit record the t/c reading during the EB weld, making a temperature sample or series of samples readable after manufacture, whenever you like.
By, 'embed', I mean the t/c and associated circuitry would be sealed inside the gozinta you are making, and not recoverable for re-use or recycling or back-calibration.



Mike Halloran
Pembroke Pines, FL, USA

 

[btrueblood]

Big chip manufacturers purposely set up a diode (or multiples of same) as a temperature measuring device - i.e. similar to a LM34 temperature sensor, which amplifies the signal from the diode forward voltage drop at a fixed current (this property varies linearly with temperature for silicon diodes). Easier to incoporate (just a resistor and a diode, plus measurement circuitry) and can be made as arbitrarily small as other parts of the circuit. I'd log to an off-board device, but it's not clear if you have any pass-thrus for instrumentation on your eb welder.

Alternatively, if you just want a "not greater than" temperature history, there are various products that can do this, though size may be an issue. Permanent temperature indicating paints, crayons, labels, etc. McMaster Carr has them, or

http://www.tempil.com/

 

[roydm]

Two things come to mind
The air pressure will be a function of air temperature

The thermocouple law of intermediate metals (have no effect on millivolts generated)
allows you to attach one wire of the junction in one spot, the other wire somewhere else.
Attach the wires by capacitor discharge welding.

Why not evacuate the cell while welding so you don't have to worry?

 

[btrueblood]

"The air pressure will be a function of air temperature"

As the OP noted, EB welding is done in a vacuum chamber.

 

[roydm]

"The air pressure will be a function of air temperature"
As the OP noted, EB welding is done in a vacuum chamber.

Fair Enough, I was thinking he wanted to know the temperature inside the cavity not the wall temperature.
If it's only a test sample a thermocouple could be spot welded inside with the leads exiting the pressure connection.

I like your Diode method