SparkFun Forums

[ebramloder]

I want to design a data-logger with PIC MCUs. This data-logger is going to work in chamber in the oil wells in the depth o 500 meters. and it is going to record temperature and pressure for 20 hours.

The pressure in that depth is about 9000 PSI and the temperature is about 130 degreeC. I want to know what kind of elements is the best elements for this project. I mean if I need a 1mF capacitor, which kind of capacitors is my best choice? Electrolytes? Polyester? Ceramics? Multi-layer? Which one is less temperature sensitive? What about the resistors? and also all the other elements.

Please shed any light you can on this issue. Any point will really highly appreciate. Does any body have similar experience?

[Ross Robotics]

You need to do a LOT of research. The type of capacitor depends on your circuit. Not only do you have to contend with the heat and pressure, but also think about the ambient gases.

No one can help you anyway since you haven't stated what data you are logging..

[Mee_n_Mac]

I can't think of many components that will tolerate, let alone operate, in a 9000 PSI environment. That's like being in the Puysegur Trench. I'd think resistors would be OK but all caps, except maybe some ceramics, would crush. Inductors would be OK, so long as they could "breathe". I'd worry that any IC would crush as there's usually a void around the actual semiconductor. Perhaps if the pressure built up slowly enough ...

Why would the electronics be exposed to 9000 PSI ? Why not put them in a "deep sea submarine" like enclosure ?

The 130 C also poises a problem. You'll find most military parts are only rated to 125 C. That doesn't automatically rule out operation at 130 C, but it will limit the power dissipation.

[waltr]

In my last job I designed circuits for 'down hole'. All circuits were in containers that where designed to take the pressure. These containers were designed by very experienced mechanical engineers and underwent extensive testing with many spectacular failures.
Mee_n_Mac is completely correct is stating that almost all electronics will crush at that pressure. I did see a number of boards retrieved from a failed pressure vessel. There were very few parts that were not physically destroyed.
This is part one of putting electronics down hole.

Part two in powering these circuits. This was done with Lithium batteries rated for high temperatures.

Last is the electronic components themselves. As Mee_n_Mac stated, even Mil Spec parts are only rated to 125°C. The stuff I designed needed to run at 180°C. Since no parts are rated to operate at this temperature every single part that might be usable required extensive testing of all parameters at the expected operating temperature. This included transistors, op-amps, resistors, caps, PCB material, potting compounds, etc.

So expect to do a lot of research and lots and lots of testing with lots and lots of failures.