Open source Sensors


#1

Hi

I am working on creating a open source underwater water datalogger for a citizens sience project (project baseline). The sensors are supposed to be deployed by divers and should be replaced regulary to get to the data and provide fresh batteries.

We have managed to get the basic logger to work (just temperature logging on SD cards), but we would like to measure visibility as well. Unfortunately all involved persons don’t know how to design this sensor.

Idealy, we could talk via I2C with the sensor and get a number from it. Since the sensor will be deployed at depth with varying amount of light (light from the surface), we need to compensate for it.

I have seen some really nice ideas - just we cannot get them to work.

Maybe someone here knows how to create this sensor…


#2

The “technical” way to do it is with a Secchi disk

but this doesn’t lend it’s self to a simple system for data logging there may be some interaction of visibility and turbidity (already open source sensors for that) as an approximation


#3

I’m curious what visibility means for this. There are various light sensors you could use (Mouser has many, many options) which could detect various frequencies of light. Are you trying to see how much light makes it way from the surface, or how much light is absorbed at a given depth (say be passing a known light source though the water at the given depth), or something else?


#4

No, I want to measure the turbidity (if that is the word). basically, the particle density in the water.

I have read that professional instruments mesure it by measuring refraction - the amount of light reflected by water.

I have seen a setup where a laser light is sent into the water and a sensor that sits beside the laser but cannot see the light source measures. To get the ambient light removed, the laser is pulsed so that you can measure the difference beteen laser on and laser off. Less light returned means better visibility.

Mapping these values to distances could be achieved by using a secci disk for calibration.


#5

Here’s one open source turbidity option: https://www.academia.edu/8319858/Open-source_mobile_water_quality_testing_platform


#6

And this one looks easy enough to build from scratch:

http://www.mdpi.com/1424-8220/14/4/7142/pdf