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Hydros 21 Gen 2 -9992 values

Home › Forums › Environmental Sensors › Hydros 21 Gen 2 -9992 values

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    • 2023-04-03 at 4:48 PM #17704
      James_NZ
      Participant

        Hi everyone,

        I have a strange error where my brand new Gen2 hydros sensor is reading -9992 for depth and conductivity.  Temperature is fine.  I have three other Gen 2 sensors deployed and they all seem to work okay (although they too have negative value drop-outs on occasion).

        I am using a Mayfly 0.5 board, and this happens in isolation of other sensor attachments.

        Has anyone experienced this?  Perhaps the sensor is faulty?

        James

      • 2023-04-03 at 8:22 PM #17705
        Shannon Hicks
        Moderator

          As long as you’re using the latest Hydros21 library file that has the longer sample time (500ms warmup and 1000ms sample time, as shown here:  https://github.com/EnviroDIY/ModularSensors/blob/master/src/sensors/MeterHydros21.h) then it sounds like maybe a faulty sensor.  Or it could be that the Mayfly isn’t waiting long enough to either warm up or wait for the measurement and you need to add additional time.  Do you have one of the Meter ZSC bluetooth interfaces for setting and checking Meter Group sensors? They’re really handy testing and troubleshooting things like their CTD sensors, and for changing the SDI12 address.

          It would be important to know whether it’s the sensor that is reporting -9992 or if it’s what the Mayfly is saying.  Sara wrote lots of code in the ModularSensors library to use -9999 as an indicator that there’s missing information (usually from a sensor or accessory).  In most non-EnviroDIY libraries, an Arduino board might report 0 (zero) when it doesn’t get any data from a sensor or peripheral device, like when a device is unplugged or missing.  But if you’ve got a sensor that can legitimately report ‘0’, for a parameter (like a conductivity sensor that’s out of the water, or a cellular board with no signal strength), then it’s important to be able to differentiate between a real zero reading and a missing sensor.

          But as far as I know, the Mayfly isn’t programmed to report -9992 for anything.  Do you only get that value when the sensor is plugged in to the Mayfly?  Does the Mayfly report -9999 for all 3 parameters when no sensor is connected?  Are you running a logging sketch or a simple test sketch?  If you use one of the simple example sketches from the EnviroDIY/SDI-12 library (like d_simple_logger) it will tell you exactly what the sensor is reporting, rather than what the Mayfly interprets.

          You could also try putting the SDI-12 address back to ‘0’ and then power the sensor and watch the serial DDI string it prints out, thus bypassing the SDI-12 libraries all together, which again can help determine if it’s a sensor issue or a Mayfly library issue.

          You should also disconnect all other external sensors from the Mayfly when troubleshooting communication issues because we’ve seen several instances of a CTD sensor losing partial or total communication with a Mayfly while a malfunctioning OBS-3 turbidity sensor was also connected to the Mayfly on another port.  Once the bad turbidity sensor is unplugged, the CTD starts working normally again.

        • 2023-04-11 at 4:30 PM #17721
          James_NZ
          Participant

            Hi Shannon,

            Thanks for your reply, and apologies for not replying sooner.  My replies to your message are in bold:

            1. Do you have one of the Meter ZSC bluetooth interfaces for setting and checking Meter Group sensors? They’re really handy testing and troubleshooting things like their CTD sensors, and for changing the SDI12 address.  – No I only have spare Mayfly boards to test this device.
            2. It would be important to know whether it’s the sensor that is reporting -9992 or if it’s what the Mayfly is saying. – I suspect there is some confusion between the data coming back from the sensor the -9999 code programmed in Modular sensors.  It seems strange that the temperature sensor works fine but not the others. 
            3. Do you only get that value when the sensor is plugged in to the Mayfly?  Does the Mayfly report -9999 for all 3 parameters when no sensor is connected? – Yes I get -9999 when no sensors are attached.
            4. Are you running a logging sketch or a simple test sketch? – I am running a logging sketch.  This sketch works perfectly for my other 9 sites. I will upload ‘d_simple_logger’ when I am next at the site to determine the raw information from the sensor.
            5. You could also try putting the SDI-12 address back to ‘0’ and then power the sensor and watch the serial DDI string it prints out, thus bypassing the SDI-12 libraries all together, which again can help determine if it’s a sensor issue or a Mayfly library issue. – Is there a sketch I could use for this, or is it as simple as setting the sensor power as ‘high’ and reading the output? 
            6. You should also disconnect all other external sensors from the Mayfly when troubleshooting communication issues because we’ve seen several instances of a CTD sensor losing partial or total communication with a Mayfly while a malfunctioning OBS-3 turbidity sensor was also connected to the Mayfly on another port. – Yes I have removed the turbidity sensor and still end up with -9992 values. 

            Thanks again for your help and I look forward to your replies.

            James

             

          • 2023-04-16 at 4:11 PM #17737
            James_NZ
            Participant

              Hi all,

              Just an update.  I uploaded ‘d_simple_logger’ to see what is coming directly from the sensor.  It seems that the sensor itself is producing the -9992 values, rather than it being created somehow by the Mayfly.

              I have contacted METER and they are looking into it.  I suspect the sensor is faulty.

              James

            • 2023-04-17 at 7:51 PM #17739
              James_NZ
              Participant

                METER replied:

                I am so sorry. That error means that there is some kind of error with the calibration of the sensor. I will have one of my colleagues reach out to you with a return material authorization (RMA)  to have that instrument brought in to have the issue fixed. 

                James

                 

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