Hello All!
I am working on a little project and I wanted to run one of the core concepts past the community here.
I do a lot of spearfishing and snorkeling, and I’d love to have a way to track and log my dives.
This little board would mount on the straps behind your mask, as the back of your head is always out of the water while you are at the surface - thus maintaining at least a
chance GPS signal.
More to the point, I’d want to add a pressure sensor so I could review depth data after my sessions.
However, there is scant information about how to build a depth/pressure gauge for a simple dive computer online.
I’M NOT USING THIS FOR SCUBA DIVING, I JUST WANT TO CAPTURE SOME DECENT DEPTH DATA.I thought maybe some people here might have experience with pressure sensors, and maybe even designing dive computers.
Does anybody have a good idea how to “directly” measure the water pressure?
What I’ve come up with is more roundabout, but perhaps more simple.
My plan is just to include a simple MEMs pressure sensor (BMP390/BMP280 etc) on the board, and then try to design an enclosure that will flex and compress when under pressure.
I’ve tried to come up with some approximate figures to estimate how much the enclosure would have to compress in order of for the sensor to detect a depth change, and I think I have some reasonable figures - assuming I’m reading these pressure data sheets right.
You can see a spreadsheet of this estimation here:
https://docs.google.com/spreadsheets/d/1DVbopse7c5WMYWjPUatB9RwQcQBXFnzpfCyu8732sfk/edit?usp=sharingI also tried to estimate the provided signal quality of the pressure sensors different mode in an iPython notebook. In the simulation I treated RMS noise as the standard deviation of the noise of the sensor output. Importantly, I don’t know how to treat the relative accuracy of the sensor. Normally it seems most sensor give noise density per root hertz, but I guess since the pressure sensors are essentially DC signals they are specified this way? Any insight would be welcome!
You can view the notebook here:
https://mybinder.org/v2/gh/ipython/ipython-in-depth/b2f9442aa52118dec44ccb0ee749ea63ac578bba?filepath=binder%2FIndex.ipynbHeres a view link in case the above interactive link doesn't work:
https://datalore.jetbrains.com/notebook/MHT5dIMlNrS6bigDKp0ahP/zqBUkd9C96g0GWiV2JrKga/What do you all think? Anybody have a better idea or method for capturing this?