High Temperature Environment

Y

YMFK

New member
Hello everyone,

after searching this forum for a long time and finding many answers for other questions I had, I finally have to open a thread myself.

I want to use a Teensy 4.1 for data logging. My problem is the temperature. I want to monitor a pump in a geothermal well, so the Teensy will be placed in a small steel enclosure (300 x 92 mm) and attachted to the pump. The whole enclosure will be submerged in 80°C water for a long period. I am not sure if the Teensy will survive in these conditions.
I plan to run it at 528 MHz but I´m not sure if that will be enough. I read in another thread that it might help to change the crystal. Are there other parts that should be changed, or could the Teensy maybe withstand these conditions without any modding?

Thanks in advance :)
Marcel
 
80 C ambient temperature is a challenge. The Teensy CPU easily adds 20 C when it’s working at 528 MHz. It has internal temperature sensors that shut it down when it sees it’s getting too hot. The trigger point for that can be increased a little bit in software, but probably not high enough for your application.
Other challenges will be:
* accuracy of RTC if you use that for time-stamping.
* finding a ~100 deg C SD card if you use that for logging.
Maybe consider this instead: https://www.netburner.com/somrt1061-and-teensy-4-1-comparison - it sort of promises 70 deg C ambient. But you want 80+…
 
Do you have anough space, power, and heat dissipation ability to consider using a Peltier device to cool a Teensy mounted in an insulated sub-enclosure? (300x92mm is a fair bit of space, but only 2-dimensional, which could be an issue :ROFLMAO: ).

Peltier devices aren't that great with large temperature differences, but if you could reliably keep the hot side to 80°C, and aim for an internal Teensy environment of 40°C, you may be OK. The key is to make sure you get rid of heat at the hot side; the better your insulation is, the less heat will flow in and need pumping back out by the Peltier. You'd also need to be fairly sure there's reasonable heat transfer inside the sub-enclosure, to avoid hot spots - multiple Peltiers may help there.

Something like https://www.sameskydevices.com/product/resource/cp061-40382.pdf may be a reasonable starting point - be sure to check out the graphs which show how the heat pumping capacity drops with increasing dT.

No doubt you'll be testing all this thoroughly at the surface before dropping it down a 1km deep well :)
 
Thank you very much for the replies!
Haha I totally forgot the third dimension! It's 18mm in height.
These are very good points! I didn't think about the SD Card, thats really something I have to consider. A Peltier element sounds like a good plan, I have to look further into that.
And yes, thorough testing will be done :) I just wanted to get a few opinions and possible solutions in advance.
 
Paul et al, any chance or interest of a Teensy industrial version using the NXP i.MX MIMXRT1061, 528MHz, ARM M7, Industrial Temperature?
 
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I just tested the Teensy in my oven. At 70°C ambient temperature it stopped working and blinked red 7 times, the internal temperature was at 90.5°C.
I am going to look more into the active cooling elements, does anyone have more ideas what I could try to make the Teensy more heat-resistant?
 
Having the Teensy at 80°C is a challenge for all parts on the PCB.
Industrial microSD cards are rated up to 85°C. With the heat produced in the enclosure I would expect that this is still critical. Maybe FRAM or so could help.

Would it be an option, to have the sensors at that place and having a cable connection to the Teensy which is at another place at a lower temperature?
How will the Teensy be powered? Can the cables to the pump somehow used also for data transfer?
Is another, industrial grade MCU an option?
 
I have ran wireline tools in high temp geothermal wells over 400 - 500F. We enclosed the tool in a stainless steel vacuum chamber, Dewar that was made for the application. Depending on the well temp we could get 8 hours or more logging time maybe that is a solution for you? National K Works (NKW) and other machine shops make these. Is this a stand alone tool or used on a electric line cable?
 
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