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High temperatures in small time

Hi everyone,
I'm a Materials Engineer from Italy trying to investigate temperatures in
fast welding and shs (self propagating high temperature synthesis)
techniques. It probably is a dumb question the one I'm about to ask but I'll
try anyway: do you know any high temperature (up to 1500-1600°C) sensors,
besides optical pyrometers and all radiation emission tecniques, capable of
revelaing huge temperature changes (up to 1000°) in 1-5 ms (milliseconds)??
Thanks a lot for your answers!
Reply to
Alessandro Fais
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In the field of Rapid Thermal Processing, accurate temperature is needed so I think this will be a good field to look towards for this kind of thermometer.
here is the first hit from googling for RTP
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MA Sonjariv
Reply to
MA Sonjariv
Do you want to record the temperature profile, meaning that real time processing isn't needed?
Or, do you want to control something, meaning that you need real time processing of the data?
Recording may be much easier than real time measurement.
One can imagine real time recording of an optical spectrum with off line processing of the spectrum to determine what the temperatures were, for example.
Reply to
jbuch
Actually RTP uses infrared/radiation measures to determine temperature, that's what I cannot do. I need an alternative for optical pyrometers.
Thanks anyway, A.Fais
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Reply to
Alessandro Fais
I do not need real time measurement (which is not so hard with a fast thermocople....very fast...). I do not need control so I can acquire data and process it later but I cannot use optical measures this is my limit. I need a thermal sensor for 100-1500°C with a response time of 0.1-1 ms!
Thanks, A.Fais
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(milliseconds)??
Reply to
Alessandro Fais
what's wrong with optical/fibre optic?
Reply to
Gung Ho
A 200 micron thick platinum foil has a time constant of about 1ms. A 2 micron foil would have a time constant of about 0.1 ms. (if my calculations are correct & I think they are).
A thin enough thermocouple should do the job for you. How large is the area to be measured?
I'd consider pounding out a hot type S thermocouple bead until it is thin enough to meet your speed criterion. You can recalibrate it for speed & thermal emf if necessary.
Start with the smallest diameter thermocouple wire your electronics can use to get the precision you need; this'll give you the smallest practical bead area when you are finished hammering.
Reply to
dave martin
you can't buy the thin thermocouple but you can make them by vapor deposition. Pt based would be easy enough. It will die in one heating cycle. It is a bit of a research project, but it can be done.
Dr. K
Reply to
William Kaukler
Oops! This is embarrassing. My estimates were not correct; a 226 micron foil will have a time constant around 1ms and a 72 micron foil should have a time constant of around 1/10 ms.
My estimates were based on TimeConst ~ density*Cp*x^2/(2*K) for constant rate heating of a slab heated from one side and insulated on the other.
K~72 w/m-K, density~21090 kg/m^3, Cp~26J/m-K, .195 Kg/m
Sorry. I hope this helps.
Reply to
dave martin
Dear Gung Ho, I'm not practical with optical/fibre optics but I guess my biggest problem would be price fallowed by the need of "destroyable" sensors. If you can give me more informations on it I would be very happy to take it in consideration (very very happy!), Thank you!
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Reply to
Alessandro Fais
This WILL help, thank you a lot. I'm working on the analogic electronics and the ATD conversion for data acquisition. Thanks again!
A.Fais
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Reply to
Alessandro Fais
Don't you think it would be possibile to get it so thin with simple plastic deformation?? Abviously I will need a recalibration after but it might be a lower cost solution...or not??
If it doesn't work although I'll take the CVD road, no doubt about it.
Thanks, A.Fais
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Reply to
Alessandro Fais
I think there's a good chance of plastically deforming it to sufficient thinness.
Heat it to medium red with a torch after each deformation to anneal it. There should be no limit to deformation if you are careful. It might help to deform it while it is hot. Use a clean, smooth anvil & hammer.
It is certainly easy to try.
Please let us know the results if you are successful or not!
Reply to
dave martin
Dr. K's solution is probably best if you've got to make a large number of these devices.
Reply to
dave martin

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