LIMIT | Everything can be measured 1
Pin meters What is known as a pin meter measures
the moisture indirectly by measuring the resistance (conductance) with an electric current that passes from one pin to the other. A pin meter measures the moisture as far as the pin is inserted. Use longer measuring pins to check the moisture farther into the wood. To measure what are known as moisture gradients, you will need Teflon-insulated measuring pins. Advantages of pin meters • Tried and tested method that has been used in the timber and construction industry for a long time. • Fast. The measurement results are displayed immediately. • Possible to detect moisture gradients. • Good on uneven material surfaces. Disadvantages of pin meters • Destructive measurement method. The pins must penetrate into the material to be able to take a measurement. • At high moisture content levels in wood, the water may be ionised together with the resin. This means that the moisture content will appear to vary. • Dependent on temperature, requiring temperature compensation for optimal accuracy. • The measurement results can be affected by impregnating agents. Some things to consider • A sledge hammer makes things easier when taking measurements with Tefloninsulated measuring pins. • Insert the pins at 90 degrees to the wood grain. • Do not measure in end grain surfaces, the cell structure of the wood means the moisture content in the ends can vary significantly when compared with the moisture content farther into the wood. Stålstift. Teflonisert stift. Advantages of capacitive moisture meters • Non-destructive measurement method, no damage to the object. • Fast. Immediate measurement results, measuring at as many locations as required. • Independent of temperature, requires no temperature compensation. Disadvantages of capacitive moisture meters • Dependent on density, material needs adjusting for optimal accuracy. • Detects rebar and other metals as increased moisture content if these are within the measurement depth and sensing range. • Requires good placement of the sensors against the material. | 131 • For repeated measurements, e.g. inspections of moisture damage, insert the pins into new holes; old pin holes will oxidise and show lower values. Capacitive/non-destructive moisture meters A capacitive/non-destructive moisture meter measures changes in the material capacitance which varies depending on the moisture content. The instrument emits a high-frequency signal. The frequency of the electrical signal will vary due to the capacitance of the material.