Mufti Esofita , MS Thesis, Dept. of Physics, Bandung Institute of Technology, 2014
We have designed a capacitance sensor in this work to investigate the correlation between wood’s capacitance value with its hardness and density. The sensor was developed based on parallel plates using copper as the elctrodes. 15 samples from five wood speciments from forest plantation that is Karet (Hevea brasiliensis), Pulai (Alstonia sp.), Pinus (Pinus mercusii), Sengon (Parasderianthes falcataria), dan fast growing teak (Tectona grandis) were tested. All of the wood samples were oven-dried to make the moisture content became 0%. The capacitance values were measured using the CV-circuit, 20 Vp-p and frequency 2.5 MHz. Meanwhile the hardness values were measured using the Janka Hardness Method. The results showed that wood’s capacitance value had a positive correlation with both hardness and density. From 25 samples (5 samples were made for each speciment) we obtained that the capacitance values are between 3,7 x 10-14 F and 6,6 x 10-14 F. Wood speciments arrangement from the smallest capacitance value is pulai, sengon, jati, pinus, and karet. This arrangement is the same if wood speciments are sorted from the smallest hardness and density to the biggest one. Wood’s hardness values are between 182 Kgf and 521 kgf, and density values are between 0,29 g/cm3 and 0,62 g/cm3. Beside that, all samples were tested in two different direction, that is tangential and radial. The designed capacitance sensor was able to distinguish measured values in both direction. The result showed that most capacitance and hardness values measured in tangential direction were greater than those in radial direction.
Keywords: Capacitance, parallel plate, hardness, wood.