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Inexpensive DO probe recommendations

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    • 2025-02-12 at 3:27 PM #18906
      Kurt@UR
      Participant

        Hi Water Quality fans,

        I would like to hear people’s experience with inexpensive dissolved oxygen (DO) probes, especially over long periods of time left in a river and if there are recommendations on what probes to use.  The desire is to keep the probe in a  river 24/7.  The application is in an urban environment somewhat hidden but still near public access so theft and vandalism is a real concern.  Therefore we need to use inexpensive probes.  Inexpensive also seems to force us to use galvanic probes, I would love someone to tell us different.

        I’ve been developing a remote DO sensor based on a LilyGOTSIM7000G controller and have a good handle on the electronics, solar charging, networking, database recording, etc.  The DO probe itself has been a struggle.   I have tried a DFRobot  and an Atlas Scientific DO probe that start out well but over weeks of use, the stability degrades,  usually trending toward reading lower then realistic values.  (Usually compared with another very expensive YSI  DO probe). Contamination, membrane damage, fresh electrolyte all have been investigated but in the end those suspects didn’t seem to be the issue. Follow ups with more controlled indoor office/lab experiments where there is no possible contamination; also seem to show these trends. We could be unlucky and just received lemon probes so if there are some DO probe success stories out there,  I think a lot of us could benefit.

        Kurt H.

         

      • 2025-02-14 at 4:26 PM #18933
        BrianJastram
        Participant

          Hi Kurt,

          In regard to downward trending DO readings, contamination, membrane damage, and electrolyte, is there an anode and cathode on your probe that you can clean? I used to use a YSI galvanic DO meter that would accumulate tarnish, which I would occasionally sand off to improve the responsiveness of the readings.

        • 2025-02-14 at 7:05 PM #18934
          Kurt@UR
          Participant

            The cathode is exposed. I did rinse the cathode when I cleaned everything and there was nothing obviously fouling it. The probe tip being under the membrane cap I considered pretty well protected. After examining my data and pictures of the probe tip, Atlas Scientific had no explanation other than saying maybe there was an unknown material inside the probe suppressing the chemical reaction. (they declined doing a failure analysis). Your suggestion is interesting. Although I wouldn’t think the probe is old enough for a typical tarnish maybe something has been coating it since the beginning. Oil, glue, plastic off gassing, all long shots but I have nothing to lose. I’ll try a bit sanding and see if something changes. Thanks.

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