@dan-wachusett Gosh just seeing this – seems like you got that Keller CTD.
Just wondering did you follow the advice given from https://www.envirodiy.org/topic/keller-ctd-sensor/#post-16332
Partly its decoding the layers of software. The keller protocol is used to access the Keller CTD map. I find it most helpful to compare and trace how different keller instruments are handled by the enviroDIY keller. If you only have one Keller Instrument on your line, then you are getting a response from that instrument – you may need to interpret the data that is coming back and find a path to getting working readings.