Soil Moisture Investigation

[last updated: 2022-04-24]
go to: Houseplant Moisture Monitor project
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• Using basic test circuit (see: houseplant project page)
  and software (...code ...) with all readings taken with same probe polarity (ie. no "flipping"),

• First test: 10 single readings in a row, with no delay between readings other than the time consumed by a serialPrint.
  Each successive reading was higher than the previous. The second reading was 10+% more than the first, the third about 5% more than the second, with decreasing increments until the 10th being only about 2% greater than the 9th.
• Next I inserted a recovery pause (100ms) between each reading.
  This gave anomalous readings, in that the second reading was like 50-70% more than the first, but successive readings only increased 5% decreasing to 1% at the 10th as before.
• Next I inserted a stabilize pause (100ms) immediately after the drive pin was turned on, and that eliminated the big jump between the 1st and 2nd readings.
• Next I turned off the drive pin in between successive readings, before the recovery pause, but that had no significant effect on the readings.

• Next I experimented with different stabilize and recovery times. With so much noise in the readings, it was difficult to be conclusive, but here's what I found:
  • The longer the stabilize period, the higher the readings.
    I tried 100 - 1200 ms.

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eof