| abstract |
A method and apparatus for detecting areas of differential density in logs, cants, timbers, poles or trees comprises applying a signal to one or more pairs of electrodes and measuring the magnitude and phase shift of the voltage, current or impedance at an output electrode. Electrodes may be arranged in a circumferential or opposed configuration depending on scanned product shape, and may be stationary or move freely but are preferably in direct contact with wood surface. Wire brush electrodes are used in some embodiments. Measurements are taken in both directions between an electrode pair. Multiple frequencies may be employed. Different electrode sizes may be used for different measurements. |