With needle and needleless moisture meters, the type of wood will affect the readings you get. For needle meters, the difference in readings is due to the different inherent resistance properties of different kinds of wood. For needleless meters, the specific gravity (SG) of the wood affects the readings.
Each hygrometer is usually calibrated with a specific species of wood, such as Douglas fir or oak, which makes the meter accurate for that type of wood but less accurate for other woods.
Generally, there are two ways to correct readings for a given species of wood:
Use the species correction table provided by the meter manufacturer.
Use a meter with built-in species correction.
Using a meter with built-in corrections is often easier and faster than referencing a manual and doing the math yourself.
