Comparison of Wood Moisture Meters Operating on Different Principles of Measurement

Abstract

This experiment compared commercially available moisture meters (three capacitive metersand one resistance meter) and tested their predictive ability at different moisture conditions on selected beech (Fagus sylvatica) and spruce (Picea abies (L.) Karst.) wood samples. The measurements were carried out on the samples at specified moisture intervals ranging from 5% to 30% moisture content (MC). The resistance meter showed a close correlation to gravimetric MC values; the influence of the measuring direction for MC below 17% was found when higher MCs in the transverse direction for both species were archieved. The difference was 4.6 times higher for softwood and 1.6 times higher for hardwood. Differences between radial and tangential transverse measuring were not observed. The close correlation coefficient of MC measurements was also found for capacitive methods. The effect of the direction was found for all the tested meters when higher MC values in the longitudinal measurements were found. This effect was especially significant at an MC of wood higher than 20 wt.%. For two capacitive methods, the effect of annual ring deflection only in the spruce samples was found where higher MC values in the tangential direction were observed.