Evaluation of Microwave and Nuclear Moisture Gages for Establishing Water Content Segregations in Southern Pine Green Veneer and Lumber

Readings obtained with a nuclear density backscatter gauge and a microwave moisture meter equipped with transmission and surface sensing heads are linearly correlated with southern pine green veneer and lumber water content per unit area g/cm2 and water content per unit volume g/cm3. These water content measures have a positive linear correlation with green weight per unit area g/cm2 and green weight per unit volume g/cm3; statistical correlations of water content on green weight are compared to correlations of water content on gage readings to appraise equipment relative efficiency in measuring water content. Microwave gage transmission sensing head readings are linearly and negatively correlated with veneer water content g/cm2 (R=0.902) and g/cm3 (R=0.889). The efficiency of this equipment increased when the average of two readings in 4-foot veneer were correlated with average water content g/cm2 (R=0.919) and g/cm3 (R=0.911). Water content was better correlated with green weight g/cm2 and g/cm3 than the surface microwave readings in veneer and with transmission and surface microwave readings in lumber. Nuclear gage backscatter readings are linearly and positively correlated with veneer and lumber green weight g/cm2 and g/cm3 and thus, with water content g/cm2 and g/cm3. The nuclear gage was more efficient in measuring green weight and water content for lumber than veneer. In lumber, water content g/cm3 (R=0.863) was measured more effectively than water content g/cm2 (R=0.846). In veneer, water content g/cm2, per 1-foot section in 4-foot veneer, (R=0.783) was measured more efficiently than water content g/cm3 (R=0.639). Four-foot veneer average green weight g/cm2 (R=0.918) was measured more efficiently by the average of four nuclear gage readings; these results indicate for veneer a nuclear gage designed to obtain readings over a larger area than that employed in the study would be more efficient.

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