How to make a moisture meter for wood

Updated November 21, 2016

Moisture meters measure the amount of moisture present inside wood, making them an invaluable tool for carpenters and woodworkers. If you try to build from under-seasoned or moist wood, the wood will shrink and dry after the item is put together, warping and cracking your piece. Though commercial moisture meters abound on the carpentry market, they aren't always easy to use or very accurate. By creating your own moisture meter, you'll know exactly what you're getting.

Lay the multimeter on a flat surface in front of you. You should see a black wire on the left side of the multimeter and a red wire on the right side. Multimeters measure direct and alternating current for electrical work. You can discover the direct current resistance to find the moisture content in your wood.

Gently unsnap the black wire from the left side of the multimeter. Place the side of a 9-volt battery along the black wire, just under the metal prong at the end of the wire. Wrap the wire and battery with electrical tape to hold them together.

Nip a 3-inch piece of copper wire. Wrap about 2 1/2 inches of the wire around the prong at the end of the black wire. Press the last 1/2 inch of the wire against the negative (larger) terminal on the 9-volt battery. Tape it in place with electrical tape.

Tap a few steel finishing nails into the wood you want to test. Finishing nails are small and won't leave a lot of damage in your wood. Place the nails at different places and depths in the wood to get an accurate reading.

Turn the multimeter knob to the left, centring it in the direct current range on the multimeter. Touch the red wire prong to each of the nails in turn.

Examine your findings. The higher the multimeter reads, the higher the wood's resistance to the direct current. High resistance indicates moisture in the wood. The multimeter should read 1.0 or lower for optimum dryness.

Things You'll Need

  • Multimeter
  • 9-volt battery
  • Electrical tape
  • Copper wire
  • Wire nips
  • Steel finishing nails
  • Rubber mallet
  • Pliers
  • Wood putty
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