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I have recently put two Mayflys with OBS3+ turbidity sensors out in the field and they are not reading correctly when confirmed with a handheld nephelometer. The low readout is reading too low and the high is reading too high. I’ve triple checked my code and the calibration curves are correct. Does anyone have any idea why this is happening? I have one other Mayfly with OBS3+ that I put out late last year that is reading perfectly.
Is the small jumper on the Mayfly board next to the Aux Analog grove ports switched over to 5v from it’s default 3v position? Did you verify that all of the sensor wires are connected to the right ports on the 6-pin screw terminal board? Red wire to Vcc, White wire to D2, Blue wire to D1, and the other three wires (black, green, and clear) all go to GND? And that the grove cable is connected to the AA0-AA1 port on the Mayfly? Do you see the red LED3 come on next to the Aux Analog ports when you’re taking a sample?
You can also post a photo of the Mayfly board and the sensor wiring on the screw terminal board if you can take a nice, focused photo.