Just checked some of my wood supply with a digital multi-meter to see if my moisture content is in the target range.
Cherry - 18 months old, spent half the time in a garage, half the time outside covered and in the sun half the day. DMM reading: 9 to 15 megohms, even on the inside of the split. Well under 20% moisture content
Sugar Maple - 18 months old, half in garage, half outside (like the cherry). DMM reading is 6-9 megohms, which equates to 16-17% moisture content.
Pine - 18 months old, stacked outside in sun and wind. DMM reading is 20-25 megohms, which equates to 15-16% moisture content.
Sugar Maple - 5 months old (fresh cut and split at that time). Stacked outside in the driveway, uncovered the first 3-1/2 months, covered last 1-1/2 months. DMM reading is 0.6 to 0.9 megohms, which equates to 24-25% moisture content.
Will have to check my hickory that is stacked in windrows in an open meadow, and now covered for the last 2 weeks. That was fresh cut and split this year, so it will be interested to see what that is right now.