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And the OBS-3 turbidity sensor doesn’t appear to be connected either, because with no sensor connected the low range value is usually around 60NTU and the high range is around 250NTU. The online Monitoring Station Manual doesn’t show instructions for how to connect an OBS-3 sensor anymore because they were discontinued 4 years ago. You’ll need either our old-style 6-terminal screw adapter board, or our newer multipurpose 6-terminal adapter board. That board gets connected to the Mayfly via the AA0-AA1 aux analog Grove jack. The wiring colors on the OBS-3 cable should be green, black, and shield all connected to ground. Red connected to 5V (be sure to move the voltage-selection jumper next to the Aux Analog Grove jacks to the 5v position (it ships in the default 3v position). The blue wires goes to D1 (or S1), and the white wire goes to D2 (or S2). If you’re using the newer multipurpose screw terminal adapter board, be sure the 3 solder jumpers on the back of the adapter board are soldered in the DEFAULT position (as shown in on of the product photos on the shop page for the adapter: https://www.envirodiy.org/product/envirodiy-grove-6-pin-screw-terminal-adapter-pack-of-5/)