@James ouch. Looking at the data file, its just the Decagon CTD/SDI-12? readings that are responding -9999 . Typically that means the (SDI-12?) protocol has failed to communicate with the instrument.
At the same time Yosemite/Modbus? is responding well.
The CTD is only occasionally failing, or failing in groups, but still working some of the time. A hard failure where it fails all the time is easiest to debug. Intermittent failures are the hardest.
You started running the setup 2021-10-25 11:16 and
then it started failing 2021-12-09 14:45
and recovered 2021-12-14 13:00
Did you do anything to have it recover?
Since then it has intermittent failures. Ouch that is the hardest to troubleshoot.
I have one LT500 that is not working well with SDI-12, its mostly failing, but sometimes works. Similarly I purchased a device that is tested to the full SDI-12 device, and its also failing a lot. SDI-12 from the Mayfly is not a standard 0-5V, so I’m planning on moving it to the Modbus. I’m also trying to figure out a way of generating a fully specified SDI-12 0-5V