Read a really good technical article in one of my boat builder mag's about the use and accuracy of moisture meters a while back.
Their conclusion was not good. (given accuracy of meter and operator)
I still like what the old time surveyor told me 30 yrs ago. " I try to bury a #2 phillips screw driver (in the days of wood boats) in it. If it sticks, walk away. If don't, buy it".