For what it’s worth, I’ve seen a video of a guy using a multimeter measuring the resistance across two pins driven into the wood at a given distance apart. How he calculated the moisture content I don’t know.
I had a buyer for some siding. He was concerned it wouldn't be dry enough and texted 47 minutes after he was supposed to leave. I asked him to confirm when he was leaving his house, for the hour long drive.
Someone else will buy it, and I was not going elsewhere this morning, anyway, so not issue. I'm getting more efficient at sticker-stacking, solo, with the least work, possible.
Loaded up another log and two halves for my neighbor to mill. Money I've had sitting in the yard, in log form. Thick, cedar fence boards go quickly. Siding is a bit less needed, as people have moved to Hardi-board siding (cement and fiber board), quite a lot .
Wouldn't be hard to compile a practical table if someone had a multimeter and moisture meter. Measure with the moisture meter, and check with the multimeter. Maybe an average of 5 readings or something, and maybe 10 samples ranging from bone dry to soaking wet. Interpolate the intermediate readings.
Making your own pinned moisture meter seems asinine... resistance varies with specie. If you were going to make your own chart you should probably take your "actual" readings with an oven test so you're not compounding errors.
Moisture over ~30% is tough/impractical to measure accurately with pin/pinless testers.
If someone with a real meter has a friend with an electronics workbench it's solved. Gator clip various resistors across the pins and voila you've got the lookup table. Don't hold the resistors with your fingers because you my friend are also conductive and Ripley's believe it or Don't you also generate voltages that will mess with the meter. It is standardized and a sort of nominally applicable average. I did exactly such with a paper moisture meter years ago. I may even have the wood lookup table.