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The coolest application of an FFT I implemented was for a custom oxygen sensor for a wearable breath measuring device. The sensor would flash a blue light at a
by roland35 5y ago
The coolest application of an FFT I implemented was for a custom oxygen sensor for a wearable breath measuring device. The sensor would flash a blue light at about 40 kHz, and there was a phosphorescent dye which would flash orange with a phase lag that changed based on temperature and oxygen level.
Using an FFT we could get that phase lag at 40 kHz and back out the % oxygen in exhaled breath! Typical oxygen sensors at the time were not anywhere near fast enough to do that.
- dr_coffee 5y agoWas the phosphorescent dye inhaled? What was the physical process responsible for the phase lag? Would love to read more about your device if you ever published your results!
- roland35 5y agoI am not a scientist so I can't pretend to understand it too well, but here is an example of a paper about it: https://www.academia.edu/17195945/O_2_pH_Multisensor_Based_on_One_Phosphorescent_Dye https://www.academia.edu/17195945/O_2_pH_Multisensor_Based_o... The dye was on a small paper disk, not in the air. It was measuring exhaled breath anyways so you weren't inhaling it. CO2 was another interesting sensor! There is a specific IR frequency it absorbs, so we used that to sense it in real time.