Reflow Oven

Speedline Technologies Electrovert OmniFlo 7E Reflow Oven OMNI7E Very Clean 2008
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US $26,500.00

Prototype SMT Line Pick Place w feeders Screen Printer Reflow Oven Package
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US $21,500.00

RTC Radiant Technology EFC 615 Convection Reflow Oven
US $17,499.99

Electrovert Omniflo10 Reflow Oven
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US $15,000.00

Electrovert Omniflo7 Reflow Oven
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US $15,000.00

Conceptronic HVA 102 High Velocity Forced Convection Oven SMT PCB Reflow Solder
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US $14,999.99

electronics in hot environments?

I want to build a data logger, able to withstand high temperatures for a short time. It should survive temps above 280c or 530f for a period of 3-4 minutes. I would like to use it every day to measure/control a reflow oven at work and it should at least live 1-3 years.
What materials would you use as enclosure ?
Why inside ? I need to check the controls/sensors of reflow oven, solder wave and need to mimic the process of actually soldering. Extrapolating data from sensors, used to set the machine, doesn't give real-time accurate data. It takes ages to tune the process just using the internal sensors. Machines are also 14-18 ft long, PCBs travel through them in one direction only, so I can't use a sensor board attached to a wire.

I'd try to tap into the oven's own temperature control circuit to get a reading or permanently fix a thermocouple in there with wires leading outside. That's existing technology.

Otherwise you're looking at some sort of ceramic material, which is going to be a pig to machine into a housing or a lining for a metal housing in order to protect your electronics/battery. Because that last one is going to be your limiting factor. You can heat up electronics pretty good for a short amount of time, but bad stuff happens in batteries when they get hot.

Edit after additional information: selling soldering equipment is actually part of what I do for a living. Not industrial size reflow ovens, admittently, but I know what's involved in the process.
I interpreted your initial question as concerning a single board, prototyping oven. A production oven is a different beast and should be installed/serviced/calibrated by a specialised company. Tuning the soldering process and keeping tabs on it yourself is indeed quite an involved activity, I sympathise.

However, if I'm allowed to leave false modesty aside for a moment, I'm also one of the best 5 practical electronic engineers in my region and, speaking as such, I can assure you developing an autonomous device, travelling through that oven to actually read "the curve" present in there with any sort of accuracy is going to be one huge headache. You simply don't want to do that unless you have a shitload of experience with electronics in extreme environments (even the people who design aircraft black boxes only know how to preserve aquired data during a fire, not how to aquire it under the same circumstances) AND you're specifically hired and payed (royally) to do just this one thing. If you have any sort of other responsibilities, decline. That's what your job is as an engineer: telling management, Q&A and R&D what is actually practically feasable, not what they think is possible based on their limited understanding of our field.

The good news is that thermocouples are generally very reliable. I did some googling (interesting thread here: http://www.smtnet.com/Forums/index.cfm?fuseaction=view_thread&Thread_ID=7046), from which I summarize the best you can do is to make sure your thermocouple connections are good, the connecting wires are good and of known specification and the computer controlling the line is interpreting the readings correctly.
When push comes to shove you know what the temperature inside the oven should be, therefore you know what the thermocouple should be reading and, if it reads significantly different, it's either the thermocouple's or the heater's fault.