[photo credit: Liz Barry. Shocked cereal box credit: D'Ignazio family]
We've been experimenting with various enclosure designs for the Riffle water monitor prototype -- our driving question being:
What's the cheapest, most accessible, effective way to keep monitoring electronics dry underwater?
One answer is: especially if you only want to measure temperature and conductivity (and, perhaps, turbidity), and log it locally inside the enclosure to a microSD card, then a 500 mL water bottle seems to be a fine choice, and pretty much ubiquitously available, world-wide:
We've recently been playing with simply using screws through the cap, rubber washers, and nuts to seal up the conductivity probes, and it seems to work nicely, for at least a week or two. My own thinking is that for a simple conductivity & temperature datalogger, this approach will be a nice, effective one for most folks to use, with the parts readily available almost everywhere.
But we've also been interested in trying other enclosure designs, for sensor probes that require e.g. cables to pass through the enclosure (some turbidity sensor designs might require this, for example).
... with the rubber fitted snugly inside the bottle mouth. I placed some wires through the rubber stopper hole, and sealed the hole with silicone sealant:
I placed this in a bottle, and then about four feet underwater in the Charles river on August 31st -- and only retrieved it this last Friday -- over eight weeks later. @liz was present to witness the slimy, smelly bottle right after it emerged from the Charles:
It was still airtight -- it hadn't leaked!
Will aim to deploy some bottles this week with the screws-in-cap option ...