The effect of frequency and temperature on dielectric properties of wood with high moisture content

Dielectric sensors are a popular choice for determining wood moisture content. However, the output of these devices, especially when measuring high moisture content, may be significantly affected by the moisture content itself, by sensor frequency (f) and by environmental temperature (T). This study investigated the effect mechanism of f and T on dielectric properties of wood with different moisture contents. Dielectric constant (epsilon) and dielectric loss factor (tan delta) for Populus nigra, Tilia tuan, Abies fabri and Fraxinus mandshurica wood samples of various moisture contents were measured from 1 to 10(7) Hz and from - 40 to 25 & DEG;C. The results show that wood epsilon increases with increasing moisture content and temperature, and decreases with increasing f. The dielectric constant depends significantly on f when T exceeds 6 & DEG;C, the rate of epsilon decreases with increasing f. At room temperature, tan delta of wood with moisture content > 50% were not related, and peaked between 10(3) and 10(4) Hz. The change of tan delta with T is complex. The results provide a basis for in-depth research on the dielectric properties of wood with high moisture content and a theoretical basis for the measurement and calibration of the moisture content of standing trees.

Automated summary

The study investigated the effect of frequency and temperature on the dielectric properties of wood with different moisture contents. The results showed that the dielectric constant of wood increased with increasing moisture content and temperature, while it decreased with increasing frequency. The change in the dielectric loss factor was more complex. These findings provide a theoretical basis for further research on the dielectric properties of wood with high moisture content and the measurement and calibration of moisture content in standing trees.