I have one for woodworking, not the prong type, and it supposedly reads by scanning into the wood. There is a chart for the different species of wood that will let you adjust your results. Bought it when I had a sawmill and it worked great for that.
Sold my sawmill years back, and really don't use it anymore. I do alot of woodturning now, and when I rough turn pieces, I weigh them. Then every week or month or so will reweigh them, and when the weight stabilizes, I know they are ready to return.
I would be willing to sell it for a very, very good price as it is just sitting in a drawer not being used. It looks as if there is a new model out now, but it last sold for $395 if my search results are right. I would let it go for $100 shipped. Enclosed is a picture of it, and one of it not against wood, and then on wood giving a reading.