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Thermochron iButtons® contain a battery and can log temperatures at regular intervals, even when not connected to a computer.  Hygrochrons log both temperature and humidity.  Each has the ability to log data all the time or only when the temperature reaches an alarm threshold.

Life Cycle: A Thermochron or Hygrochron use has a definite life cycle that follows these steps:

1) A plan is developed for the use of the device.  The plan will include the following:

    1. A description of the mission.
    2. What temperature and/or humidity ranges are required to be logged.
    3. Accuracy required. 
    4. How often the data should be logged.
    5. The length of time of the missions.
    6. What is the acceptable range for the data.
    7. If data should be logged all the time or just when the data is out of an acceptable range.

      Maxim provides an application note with more information about the mission parameters.

      2) The data logger is programmed for the mission using a special software package and a 1-Wire® master.

        • A free software package is available from Maxim and is effective for small batch programming.

        • Thermodata Viewer is a more complete solution that provides better batch programming and data viewing. 
      A "master," or interface device, is required to allow a computer to talk to the data logger over the 1-Wire® bus.
        • A LinkUSBi is included in the Thermodata Viewer package, so you may be all set if you ordered the package.
        • A LinkUSBi will provide connectivity through an USB port for other software as well.
        • A Link45 will provide connectivity through a serial port for any of the above software.
        • A Maxim DS9490R (USB) or a DS9097U (serial) may also be used.

      A cable and probe are used to connect the data logger to the master.  Any of the following probes will work:

      3) The data logger is sent on the mission to collect data.

      Please note that the data logger is not waterproof.  Do not directly bury in moist soil or place in water.

      You may protect your data loggers through an iButton® Capsule, certified to "Water Resistant 3 ATM Requirements."

      4) The data logger returns from the mission and the data is retrieved.

      The same software and hardware used to program the mission is used to retrieve the data.

       

      Thermochron/Hygrochron models vary in the following ways:

        • The operating temperature range.
        • The amount of memory available for storing data.
        • The accuracy of the temperature reading.
        Please review the chart below for details on the different Thermochrons available.

        Thermochron and Hygrochron

        COMPARISON CHART

        Both measure and datalog temperature in various ranges and accuracy.

        Hygrochrons measure humidity in addition to temperature.

        Model

        Temperature Range Accuracy Resolution Values / Readings Logging Rate PDF Data Sheet

        DS1921G

        -40°C to +85°C +/- 1°C: -30°C to +70°C
        +/- 1.3°C outside this range
        0.5°C 2048 1 to 255 min

         Data Sheet

        DS1921H +15°C to +46°C +/- 1°C 0.125°C 2048 1 to 255 min Data Sheet
        DS1921Z -5°C to +26°C +/- 1°C 0.125°C 2048 1 to 255 min Data Sheet
        DS1922E +15°C to +140°C +/- 1.5°C:  110°C to +140°C
        +/-7°C is typical from 15°C to 110°C
        Programmable
        0.5°C - 8bit / 0.0625°C - 11 bit
        8192 - 8 bit or 4096 - 16 bit 1 sec to 273 hrs

         Data Sheet

        DS1922L -40°C to +85°C +/- 0.5°C:  -10°C to +65°C
        (with software correction)
        Programmable
        0.5°C - 8bit / 0.0625°C - 11 bit
        8192 - 8 bit or 4096 - 16 bit 1 sec to 273 hrs

         Data Sheet

        DS1922T 0°C to +125°C +/- 0.5°C:  +20°C to +75°C
        (with software correction)
        Programmable
        0.5°C - 8bit / 0.0625°C - 11 bit
        8192 - 8 bit or 4096 - 16 bit 1 sec to 273 hrs

         Data Sheet

        DS1923 Hygrochron -20°C to +85°C Includes 0 to 100% humidity logger +/- 0.5°C:  -10°C to +65°C
        (with software correction)
        Programmable
        0.5°C - 8bit / 0.0625°C - 11 bit
        8192 - 8 bit or 4096 - 16 bit 1 sec to 273 hrs

        Data Sheet

        NASA is using Thermochrons for the History of Winter program.  Take a look to see some serious Thermochron use!

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