Timber moisture measurement
Portable timber moisture meters
Resistive moisture metersWood moisture level is inversely proportional to the electrical resistance measured between two points: the more moisture there is, the less resistance.
Defined by the EN 13183-2 standard for sawn wood and surfaced lumber, the resistivity measurement is based on the circulation principle of an electric current. Electrical resistance moisture meters measure wood between two electrodes. With insulated pins, these moisture testers allow wood measurement at different depths without taking into account surface moisture.
Capacitive moisture metersWhen held against the wood surface, the moisture tester emits a high frequency signal. It interprets the reflective or absorbent level of an electrical field, based on the temperature and the moisture of wood. This method of measurement must be carried out on a flat surface.
Wood oven dryingThe oven drying method for measuring timber water content consists of taking a wood sample (from 100 to 200 g), weighing it then drying it.
The wood moisture content (%M) is then measured using the formula:
%M= (wet wood mass-anhydrous wood mass/anhydrous wood mass)*100%.
This method is stressful and destructive to wood.
Moisture measurement and durabilityWood moisture content or water content is a key parameter for the structural durability.
Whatever moisture measuring method, producers must comply with standards in force and put in place a Factory Production Control (FPC) system, so as to ensure compliance of the wood products they put on the market.
Also, to comply with the EN 14081* standard, they must guarantee the skills of all staff responsible for classifying wood and for checking moisture measuring instruments used in sawmills that produce wood for wooden structures.
Renewable resource, the wood used in construction, timber, contributes to reduce greenhouse gases, CO2 in particular, by trapping carbon.
* Law dated 3 July 2006 relating to some wooden structures
This timber moisture tester is designed for measuring framework, sawn lumber, slicing wood as well as wood panels.
"pricing depends on the measured moisture content"
Fibre saturation point
When free water has evaporated from the wood cell lumina, water bound to wood cell walls remains.
The corresponding equilibrium moisture content is approximately 30% in most wood species and is called the "fibre saturation point" or FSP.
Equilibrium humidity content
Also known as the hygroscopic equilibrium, this term is used to define the water equilibrium of a material in relation to external conditions.