William W. Moschler

Microwave Moisture Measurement System for Hardwood Lumber Drying

The goal of this project was to develop a prototype microwave-based moisture sensor system suitable for the kiln drying of hardwood lumber. The moisture sensors developed are battery powered and are capable of communicating with a host kiln control system via spread spectrum wireless communications. We have developed two designs of the sensors working at 4.5 to 6 GHz with linear response to moisture content (MC) over a range of 6–100%. These sensors allow us to make a swept frequency microwave transmission measurement through a small area of a board. Using the prototype electronics and sensors, we have obtained measurements of MC over the above MC range for red oak and yellow poplar with standard deviations of less than 1.5% MC. We have developed data for board thickness corrections and for temperature corrections for the MC measurement system.

Dynamics of mat consolidation during pressing: what we've learned with our in-press radiation system for pressing wood composites

We have designed a radiation-based system for density measurement of wood composites during pressing. During pressing, heat and mass transfer, consolidation speed and mat characteristics interact to produce a density distribution in the mat that is typified by high surface density and low core density. Measuring density of the wood mat during consolidation is a key parameter for understanding subsequent product performance. The system provides for density measurement at three horizontal planes in the wood mat, at positions of 25 percent, 50 percent, and 75 percent of the mat thickness at any time during the press cycle. The system incorporates three cesium sources and electronic detection equipment, collimated to move in concert with the up-acting press platen. Radiation count data taken at eight counts per second is converted to density. Press position and time are simultaneously recorded with the count data. Experimentation with the system has included radiation measurements in aspen and pine wood mats, incorporating different rates of press closure and furnish moisture content; both variables known to influence formation of the density distribution in the mat. Results are presented that depict density changes in the mat during pressing.