I think we will be able to purchase one Keller CTD this year and I will work on getting it going on the Mayfly 1.1 in whatever spare time I can find in my schedule. I appreciate all the input so far and I am looking forward to digging into this in the coming months. I will keep you both posted as I get going… I’m sure there will be lots of questions. Gathering any necessary hardware will be the first step, so I will check out the RS485 driver wing board you mention above. Unfortunately, working for a government agency makes it rather impossible for me to purchase additional sensors for testing/development.