The wood NDT laboratory of the University of Western Hungary, Sopron has developed the DYNAMOE lumber grader. The machine measures the dynamic modulus of elasticity (MOE) and specific gravity of the lumber, The strength grades of structural lumber is defined by the EN-338 standard. The standard is based oil the MOE and specific gravity. The dynamic MOE is calculated by the well known formula: specific gravity multiply by the stress wave velocity square (M0E_dyn=rV²). The static MOE is predicted using dynamic MOE and characteristic time given in (Divos and Tanaka, 2000). Stress wave is induced by a hammer impact on the end of the lumber. The vibration is picked tip by a microphone. The microphone and balance signal is recorded by an analogue to digital converter card The AID card and the microphone amplifier together with the balance electronic is located inside of the extension unit of the computer. Figure 1. shows the DYNAMOE system: computer, extension unit, microphone and balance.

The recorded vibration is appears on the up right corner of the monitor. The longitudinal eigen-frequency of the lumber is determined by the Fourier spectra of the vibration. 512 point digital FFT algorithm is applied. The stress wave velocity is calculated by the eigen-frequency and the length of the timber. After the hammer impact the balance measures the weight of the timber and calculates the specific gravity using pre-set dimension data. The test takes less than 3 seconds. Using appropriate balance DYNAMOE can test small specimens or large glued laminated timbers is well.