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ESP32 not reading SDI12 Implexx sap flow sensor when 35oC

Home › Forums › Other Data Loggers › ESP32 not reading SDI12 Implexx sap flow sensor when 35oC

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    • 2023-02-17 at 1:27 AM #17609
      FHB-logger
      Participant

        I have a data logger using the ESP32 and using the EnviroDIY SDI12 library.  The library has read all the SDI12 devices I have (Enviroprobe, Sentek probe, Terros 21, Implexx fruit size dendrometer and Implexx trunk dendrometer) successfully except one, the Implexx Sap flow sensor.  It cannot get readings from the sensor when the air temperature exceeds about 35 oC , I use the C and D commands.  It mostly fails on the first ?C! command, so it does not continue to try and read.  I have forced it to try and read after a failed ?C! command but no data is returned.  On occasion the ?C! will respond and I only get data from the first or second D reading (?D0! or ?D1!). The ESP32 does not feel overheated when I touch it (it does not heat up itself), it just feels warm as any other object would in 35oC + heat.  The logger and sensor are not in the direct sun (shaded).  All other SDI12 devices keep on reading when the temperature rises, except the Implexx sap flow sensor.  When the temperature cools down the sensors start to read again, although some need the ESP32 to be reset . Implexx tell me they have not had any problems with their sensor with other data loggers. When a cooler day comes I will conduct a test by heating up the separate components to identify the issue and I am seeking clues if anyone else has experienced a similar issue and suggestions. One thought is does the SDI12 commands timing sent out by the ESP32 change slightly with temperature and if so can this be corrected?

      • 2023-02-17 at 3:14 PM #17610
        Shannon Hicks
        Moderator

          What board are you using for your datalogger?  And what is your battery and the model of the ESP32 you’re using?

        • 2023-02-17 at 7:00 PM #17611
          FHB-logger
          Participant

            It’s a custom data logger that for the SDI12 connection basically connects pins to  screw terminal. We are using a 12v 16 ah sealed lead acid battery. I did try 5v  nimh with a 1A setup 12v buck previously and it had problems with the sap flow. All other sensors work fine with the stepup. I am using the EZSCB ant esp32. It has the lowest sleep power usage. I have just shallow buried the electronic box ( keep constant temperature) and insulated the probe on the tree. We will get some days next week in the 39oC so this will test if the issue is on the sensor side.

          • 2023-02-20 at 9:21 AM #17612
            Shannon Hicks
            Moderator

              Without knowing more about what board you’re using for the logger, or the software that runs on it, it’s hard to guess what the problem is with your system.  But I know that when we first used Arduino Uno boards for loggers about 10 years ago, we found that they became unreliable and inaccurate at high temperatures, both in terms of timing and analog voltage measurements.  And if your logger or various components are specified to run at 5 volts, but you’re powering things with a 12v battery, then whatever voltage regulators are on the boards are having dissipate a lot of heat in order to drop the supply to 7 volts.  That heat, along with hot ambient temperature, could be causing issues too.

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