How Does a Moisture Meter Work?
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Timber and Boards
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Moisture meters are hand-held devices that monitor the percentage of moisture in wood. These type of meters are a valuable aid not only for the processors of wood products such as mill sawyers and cabinetmakers, but the home shop woodworker as well. The small moisture meter can reveal if a board or wood product has too much moisture in the material. A heavy amount of moisture can mean that the piece may not fit correctly in a tight joint or expensive work piece. Mill sawyers use a moisture meter to identify certain logs that are properly cured for cutting into expensive boards. The mill can also use the moisture meter to tell them if the drying process is on schedule as in large heated kilns for removing moisture from stacks of lumber.
Moisture and Electricity
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Electrical power is easily conducted through a moist or wet environment. When wood fibers contain moisture it can also conduct an electrical signal or voltage. This allows the moisture meter to act as a signal generator. The signal generator will output a small voltage into the wood fibers. The small voltage is typically supplied by a battery. The moisture meter contains an internal circuitry much like an ohmmeter. The ohmmeter reads the amount of resistance that an electrical circuit may employ in conducting electricity. Resistance is the opposing force to efficiently conducting electricity. The moisture meter will send a small voltage into the piece of wood being tested. The voltage is conducted into the piece of wood through two very sharp pins. These pins are set a specific distance apart from each other and when the test button is pushed the meter can read the resistance between these two pins. The resistance of the wood fiber circuit is then transferred to an indicator.
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LCD or Analog
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The indicator can be in the form of an LCD screen or a simple analog type meter. The LCD screen may give a numerical display as to how much moisture in that particular piece of wood. The analog meter will deflect a needle to a corresponding number on the face. These numbers will correspond to the percentage of moisture in the wood fibers. Large boards may have to be tested in a number of locations as the small pins are generally one inch apart from each other. This means that the meter is only reading that small portion of the boards moisture content. Moisture meters range in price from below $50 to units that can be tied to a laptop computer for thousands of dollars. Regardless of the cost, all moisture meters will give a reading as to the amount of moisture that is contained in a piece of wood.
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