Moisture in Wood: Meter Usage Helps Avoid Problems
March 6, 2013 | 12:22 pm CST

Moisture in Wood: Meter Usage Helps Avoid ProblemsWhether you use a pin or pinless variety, moisture meters can help prevent warping and shrinkage in wood products.

Moisture meters are essential tools for avoiding wood problems such as shrinking, warping and cupping. With both pin and pinless meters available, it is not an easy choice between the two types. Both have advantages and disadvantages.

Moisture in Wood: Meter Usage Helps Avoid ProblemsPinless meters use electromagnetic wave technology, which measures the density in a 3-D field underneath the measuring pad and indicates the average. While both types of meters must take into account the wood species, the wood’s temperature does not affect the measurements in the pinless meters, therefore no correction is necessary.

One of the advantages for pinless meters is that a large number of boards can be scanned in a short time and the measurements leave no visible marks, i.e., no pinholes. Even though pinless meters do not indicate differences between surface and core, the meters can detect water pockets and higher moisture levels across the board.

However, pinless meters require a somewhat flat and smooth surface. The measuring area should be at least as big as the measuring pad on the meter. Also, the measuring depth is crucial. Moisture values are too low for materials thinner than the measuring depth. And the pinless meters cannot read any deeper than the measuring depth indicates.

Moisture in Wood: Meter Usage Helps Avoid ProblemsPin meters measure the electrical resistance between two pins. The electrical resistance changes with the moisture content of wood — if moisture varies within the small segment of the non-insulated part of the pins, the highest value is indicated. Also, if lumber is hot or cold the electrical resistance in the wood changes; therefore, temperature corrections are necessary.

For thorough quality control, moisture should be measured down to the core. The slide-hammer electrode with Teflon coated pins is the ideal tool. As the pins are hammered towards the core, consecutive measurements indicate if the wood is dried to the core. Meters measure down into the board, even if the boards are several inches thick. If only small meters with integral pins are available, core readings can be obtained by cutting the wood and measuring the end grain.

As for general usage, the pin meters are more versatile. Every piece of wood wider and longer than the distance between the pins can be measured, including round, small and oddly shaped pieces.

If measurements are taken before or during the manufacturing process, it may be easy to hide the pin holes. If the product is already finished and the moisture content needs to be checked, a pinless meter could be the best choice. Regardless of using pin or pinless meters, it is strongly recommended to check the moisture content when drying lumber, buying or selling wood, making furniture and cabinets or dealing with hardwood floors.

Source: Lignomat USA. For information visit or call (800) 227-2105.

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