Welcome to EnviroDIY, a community for do-it-yourself environmental science and monitoring. EnviroDIY is part of WikiWatershed, an initiative of Stroud Water Research Center designed to help people advance knowledge and stewardship of fresh water.
New to EnviroDIY? Start here

Reply To: Hydros21 Reporting -9999 on Mayfly 0.5b

Home › Forums › Mayfly Data Logger › Hydros21 Reporting -9999 on Mayfly 0.5b › Reply To: Hydros21 Reporting -9999 on Mayfly 0.5b

2026-06-11 at 1:48 PM #19705
caroline@wachusett
Participant

    Hi Shannon,

     

    Thank you for the response. I ran the board attached to my computer in Arduino and the red LED3 light did come on when the sample was run. I put a voltmeter across the GND and V pins and the voltage was 3.3v when the sample was collected. It still was reading -9999 when this test was run (with the old sensor attached to the board).

     

    The sketch on the 0.5b board is older than 2022 so that would explain why the new Gen2 sensor did not work. The sketch on the 1.1 board is from 2025.