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Increasing resolution and reading differential voltage

Home Forums Mayfly Data Logger Increasing resolution and reading differential voltage

This topic contains 4 replies, has 3 voices, and was last updated by  Iris Allen 3 months ago.

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  • #12208

    Iris Allen
    Participant

    Hi!

    I’m looking to use the mayfly data logger to read data from my homemade sap flow sensors. To do this I need to increase the resolution so I can read up to 0.0001 v of differential voltage. I know there are ways to increase resolution and read in differential voltage, I’m just not too sure how to get started. I currently have the mayfly starter kit; would I need to purchase any addition hook ups to make this work?

    Thanks in advance!
    Iris

  • #12209

    Shannon Hicks
    Keymaster

    The Mayfly has an ADS1115 16-bit A/D converter on it. To use it, you can use the Adafruit ADS1x15 library and follow the tutorial on this page: https://learn.adafruit.com/adafruit-4-channel-adc-breakouts?view=all

    The library comes with examples for single-ended and differential measurements. So you can follow the differential example to take a reading with the Mayfly. The ADS1115 on the Mayfly is at the default I2C address of 0x48. Using the default gain of 2/3, you’ll have a resolution of 0.1875mV per bit. So if you want 0.1mV resolution, you need to switch the gain to 2 so you’ll get 0.0625mV per bit. But that also limits the range of the maximum input voltage, so be careful not to exceed it. Exact details about the resolution and gain settings can be found in the example sketch that comes with the library.

  • #12210

    Iris Allen
    Participant

    Shannon,

    Thanks for the help! I’m going to start messing around with it this week, so I might come back with more questions soon.

    Thanks again,
    Iris

  • #12243

    Dave
    Participant

    Iris,

    I’d be interested to hear what you find. Here in NH we have interest in sap flow measurements for projects in conjunction with the Proctor Maple Syrup Institute at UVM. Installing Mayfly-based networks could be really interesting to them.

    Dave

  • #12249

    Iris Allen
    Participant

    Dave,

    We should get everything with the Mayfly up and working within the next month, so I’ll keep you in the loop!

    Iris

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