'No-Parts' Temperature Measurement with a Pro Mini

A project log for The Cave Pearl Project

Creating a generic underwater data logging platform that is easy to build & modify for many different environmental monitoring projects.

Edward MallonEdward Mallon 02/25/2019 at 14:424 Comments

Temperature is so fundamental that it doesn't get a lot of love in Arduino land, compared to sexy IMU's or spectral sensors. So there aren't many digging through the white papers for other methods to measure  molecular jiggliness. But I found an interesting method using the WatchDog timer and it turned out to be far easier to rework for a Pro Mini than I would have expected.

'No-Parts' Temperature Measurement with Arduino Pro Mini

Works far better than the two clocks method I tried last year.


Edward Mallon wrote 02/26/2019 at 05:59 point

I missed a very important aspect of the two clock method in my earlier post - there is about 50 points of inter reading  jitter which translates into about 0.1C of noise.  I made the resolution claim based on the delta, which really is there, but I was not zoomed in enough to catch the noise issue. I will be working on that over the next few days to see if I can't get it under control with better timing, and/or more power reduction during the sleeps.  Also wondering if the no-interrupts during the sleep causes a few miscounts on the timer0 overflow...?

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Edward Mallon wrote 02/25/2019 at 18:44 point

also... I can apply this as a software patch for all the sensors already out in the field...

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Edward Mallon wrote 02/25/2019 at 17:39 point

Ha!  Without knowing you did that, I added it as a comment to your project post about the TMP sensors. Ships crossing in the night... :-)

Unless I discover some really weird aging or hysteresis effect, this technique will replace the thermistors I've been using to date for my loggers ambient temp. record. Since I test everything for a week before deployment, the calibration effort is pretty much the same.

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Jan wrote 02/25/2019 at 16:40 point

Hi Edward. Fantastic write-up as usual. Just submitted it as a tip at

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