I don't know much about moisture content meters, but I've always used the same oven method I use in the laboratory. You'll need a drill, a 1/2" or so auger bit, a kitchen scale, oven, and an oven-proof dish. I first drill into the end of the log an inch or so discarding those shavings. Then, continue to drill a ways further and collect the shavings. You'll want quite a few so you get a representative sample. In big logs, you might want to drill several holes. In smaller logs, drill one or two holes in several different logs to get a representative sample. Keep the shavings in a ziploc bag until you're ready to weigh them. After you've collected your samples, weigh your oven proof dish on the kitchen scale (I use a foil pie pan since it's light and disposable). Record that weight, then put your shavings in and record the weight again. The difference is the weight of the wet shavings. Then, put the shavings in the oven at ~225 degrees for a few hours. I then reweigh the pan with the shavings and record the weight. Next, put the pan back in for 30 minutes or so and weigh again. If it is the same as before, you're done. If it has dropped, then put back in and repeat. When you have 2 weights that are almost the same, you're done. Subtract the weight of the pan from the weight of the dried shavings and you have the weight of the dry shavings. The difference between wet and dry shavings is the moisture content. Do the math from there and you have the % moisture.
This method will sometimes bias a little high on woods with a lot of volatile oils, as you'll be counting the weight of the oils as moisture weight. I had a research project involving cedar wood once upon a time and found this oven method to bias a percent or two high (when compared with Karl Fischer titration moisture content) on that wood. Hardwoods have always come out pretty close.
FYI, I discard the outer inch of the wood so surface conditions (high or low relative humidity, mainly) don't influence the moisture determination of the log itself.
