Problems with OBS3+

This topic has 3 replies, 2 voices, and was last updated 2020-09-21 at 10:08 PM by Shannon Hicks.

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- 2020-08-31 at 2:28 PM #14545
  jsterling
  Participant
  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.
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  Turbidity_OBS3.png
- 2020-08-31 at 4:38 PM #14547
  
  Shannon Hicks
  Participant
  
  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.
- 2020-09-21 at 4:42 PM #14591
  jsterling
  Participant
  It turns out that I had had wires of the OBS3+ in the wrong screw terminals. Rewiring the high and low turbidity readings within a reasonable range. The problem now is that the sensor is not reading accurately. High turbidity always reads about 3 NTU and low turbidity always reads about 1 NTU. I have measured with two handheald turbidity meters and they were both reading 11-12 NTU. I checked and the grove cable is connected to the AA0-AA1 terminal and the aux analog port is switched from 3V – 5V. I’ve attached a photo of my wiring. Thanks!
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  IMG_0239-scaled.jpg
  IMG_0238-scaled.jpg
- 2020-09-21 at 10:08 PM #14594
  
  Shannon Hicks
  Participant
  
  It sounds like the sensor isn’t getting power. Do you know which sensor wire you had plugged into the Vcc jack on the screw terminal board? Do you have a voltmeter (multimeter) that you could put on the Vcc line to measure the output voltage of the Mayfly’s 5v switch boost circuitry when the sensor is supposed to be powered for a sample? It’s likely that connecting the sensor wires to the wrong terminals damaged the circuit on the Mayfly board that generates the 5-volt power, or the sensor itself might have been damaged.
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