A Beginner’s Guide to Buying the Correct Moisture Meter
People who work with wood as a raw material know how moisture can affect the outcome of the final product. Generally speaking, a newly cut log has at least 80 percent moisture content (MC). It needs to be dried before it can be turned into a piece of furniture or be used as fuel for a wood burner. To determine if it has reached the proper amount of moisture, you will need to use a MOISTURE METER.
What is Moisture Content?
Moisture remains in the wood’s fiber even after it has been air dried or kiln dried. It affects the wood’s durability and strength during the course of its lifetime. As the log is being processed into lumber, the wood is dried to reach a specific MC. The goal is for it to be in balance with the temperature and the relative humidity (RH) of the environment where it will be used. If it’s going to be turned into a table, for example, will it be placed indoor or outdoor?
With high RH in the surroundings, the wood expands as it absorbs water. With low RH, it shrinks as its moisture is released into the air. This is a normal occurrence. However, if there is an extreme moisture condition, big cracks can appear on floor boards and surfaces can become uneven. There may also be a failure in veneering and laminating, or appearance of fuzzy grain.
What is Equilibrium Moisture Content?
In a normal environment, the wood gains or loses moisture until a time comes when the amount of water it contains is in equilibrium with its surrounding environment. This is called the Equilibrium Moisture Content (EMC), or the baseline wherein the piece of wood is neither losing nor gaining moisture. The equilibrium may change depending on the humidity and temperature (i.e. your current season, amount of rainfall, etc.), but you should still be able to find the baseline. Once it reaches this states, it means you can already use it as needed. The use of a WOOD MOISTURE METER will provide you information about how the structural stability of your end product can be affected by the wood’s MC.
To get the EMC, hang thin scraps of wood in the area where you normally work, such as the shed with your carpentry equipment, or the area where you store your firewood. For a period of time, take a daily reading and then get the average result. EMC is important to people who use wood for making furniture or wood flooring because it helps them determine if it is appropriately dry for its planned purpose and project design. For instance, wood flooring installers will have to verify that its moisture content matches the building interior’s relative humidity.
What are the Kinds of Meters Available?
Pinless Meter
This tool is used to compare the wood’s electrical properties in relation to the water it contains. The principle is called capacitance, which is the ability of an object to carry an electrical charge. (And as you may know, water is highly conductive of electricity, while wood is not.) A pinless meter will be able to determine the moisture on the surface or shell of the piece of wood, but not much about the moisture toward its center. In this regard, the tool is appropriate for a plank of wood or a thinner piece, as well as a three-dimensional space, such as a plaster wall.
To use this DAMP METER, turn it on and place it on the surface of the material. If your device can be programmed depending on the type of wood you want to test, then ensure you select the correct setting for the specific species prior to using it. If the meter cannot be programmed this way, you will have to check the species adjustment table that is provided by the manufacturer. Once you place it on the surface, the moisture content reading will be displayed on its screen. Depending on the model, the screen type can be digital, analog, or LED.
This tool also needs to be calibrated for it to deliver a precise MC reading. Normally, the manufacturers also sell calibration verification blocks so you can tune your pinless meter on the job site.
Pin Meter.
This device has two metal spikes located at one end, which you will have to insert into the piece of wood to take a reading. The spikes enable the tool to get a truthful measurement of the wood’s overall MC (shell and core), which makes it perfect for people who need to test logs for stove fuel. They need to know if the core’s MC is just right (about 20 percent) because if the log has too much moisture, it will produce a lot of smoke, but less heat. The more heat a log produces, the less amount of wood needs to be fed into the stove.
Although this meter can also be used by a woodworker, he or she will prefer the pinless device since it will not damage the material he or she is working on. A woodworker will want the finished furniture to have no higher than 8 percent MC so the constructed piece will be tight and solid. If the wood’s moisture content is high during the time it is being assembled as a drawer, for example, the parts may not fit properly in the future if the wood dries out.
Another disadvantage of a pin meter is the risk of breaking the spikes, since you will have to use force when inserting them to the wood. The longer pins you have, the greater chance they will break during use. The pins can be replaced, but if you don’t have a spare, then the tool becomes unusable.
Your pin meter also needs to be calibrated. If it’s out of calibration, change the battery and see if it will work. If not, bring it to a professional for repair.
