FAQs about wood moisture measurement

FAQs about wood moisture measurement


Wood moisture meters for industrial & mill applications – questions & answers

Why Should I Use A Moisture Meter?

Structurally sound and beautiful in appearance, wood is the ideal raw material. Delmhorst customers in the woodworking/lumber industry know that moisture content is the single most important factor affecting the quality of their products.
To ensure quality, from the mill and dry kiln to the finishing floor, Delmhorst moisture meters help minimize defects such as shrinkage, cracks, and splits. Years of experience, high-tech tools and controls, and premium grade lumber cannot make a difference if moisture content goes unchecked.

Are There Different Types Of Moisture Meters?

There are two types of moisture meters commonly used in lumber and woodworking applications.
A pin-type uses two pins that penetrate into wood at the users desired depth. Pin-type meters are the only instruments that indicate the moisture conditions inside a board or a piece of wood. Using insulated pins, only the uncoated tips are exposed to the wood fiber, providing more accurate readings of moisture content at various levels of penetration. Using a pin type meter with insulated pins is still the most effective method to determine moisture gradient, which is the difference between shell and core moisture content.
Pinless moisture meters read moisture closest to the source of the magnetic field, in this case, at the surface. For quickly scanning finished product, a pin-less meter is a convenient way to identify a problem area. However, a pinless meter cannot differentiate between shell and core moisture content and will not detect a moisture gradient. Also, readings provided by a pinless meters are affected by surface moisture.
Please refer to the diagram below for a basic look at the difference between readings obtained from a pin-type meter compared to a surface meter.
This diagram illustrates that pin-type meters and surface meters provide different information about the moisture content in a board. Each technology may be appropriate for different applications. Before choosing a meter, it is important to understand these differences in readings and choose the type of meter best suited for your particular application.
How Does A Moisture Meter Work?

Using the principle of electrical resistance, pin-type meters use the board as an element in a circuit by driving two pins or electrodes into it. This method works because moisture conducts electricity well and dry wood is an effective insulator.
Most pinless meters use the capacitance method, which uses the relationship between the moisture content and the dielectric properties of the wood.
Both the resistance and the dielectric properties of wood change in direct proportion to its moisture content, within a specific range

In What Range of Moisture Content do Pin-Type Meters Operate?

Resistance-type meters express moisture content as a percentage of the oven-dry weight of the wood. These meters work best from the range of fiber saturation point (25 to 30 percent) down to around 6 percent. Below 6 percent, it’s tough to make accurate, repeatable readings because of the high electrical resistance in really dry wood. This is particulary true at low relative humidity levels, generally below 30 percent.

Electrical accuracy of all Delmhorst meters is better than 0.5 percent between 6 and 12 percent moisture content; better than 1 percent between 12 and 20 percent moisture content; and better than 2 percent between 20 and 30 percent, or at fiber saturation point. You can check accuracy either through the internal check or with a Moisture Content Standard.

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