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Ultrasonic guide User ? s Guide FAKOPP ULTRASONIC TIMER www fakopp com CIntroduction Ultrasonic velocity is a basic parameter for nondestructive evaluation of tree seedling wood veneer wood panel products and concrete Defect localization and material prop

User ? s Guide FAKOPP ULTRASONIC TIMER www fakopp com CIntroduction Ultrasonic velocity is a basic parameter for nondestructive evaluation of tree seedling wood veneer wood panel products and concrete Defect localization and material property determination is possible by measuring ultrasonic velocity This equipment designed for veneer and seedling tests Operation principle Two identical piezo-electric transducer is connected to the material A short ultrasonic impulse is generated by electronic excitation of the transducer and at the same time timer starts running The sound propagates in the material and after a while reach the second transducer The signal of the second receiver transducer stop the timer when the signal reaches the threshold level V see ?gure The transit time appears on the screen of the equipment in microseconds excitation pulse received signal Amplitude v Time s - - - thres hold measured time signal atlaiutmmuddpleie-- Figure Timer starts when excitation pulse rise and stops when received signal reaches the threshold level The received signal polarity is opposite in this unit CTime correction The transit time appears on the screen includes the transit time inside the transducer The wave guide triangle or spike is part of the transducer If we measure the distance between the screw locations center of triangle wave guide we have to subtract s from the readout to get the correct transit time in the sample Using this corrected time and distance data correct ultrasonic velocity determination is possible Distance de ?ned as the distance between the transducer center see ?gure Distance Figure Distance determination Determination of the time correction is done by the following technique The read out time is recorded while distance between transducers vary between and cm The material used for the test was sound spruce lumber The intercept of distance - read out line determines the time correction See ?gure The intercept and the time correction is A theoretical determination of time correction is based on the stress wave velocity in aluminum and the total length of the sound path in aluminum Velocity is m s at room temperature and the distance is m The calculated time t s e g s This value is in a good coincidence with the measured data s Ctime s y x R distance cm Figure Measured time as a function of distance Velocity determination V m s distance mm read out s -time correction Time correction for transducers equipped with spike Distance between transducers is measured between the points where the transducers are inserted into the seedling The penetration depth of the spike e ?ect the time correction We applied mm penetration depth measured in spike direction distance Figure The applied setup for seedling test Ctime s y x R distance cm Figure The time correction determination Conditions material green willow branch spike penetration was mm The measured time correction according to ?gure is s Installation This section describes the installation step by step Connect two pieso-electric transducer's cables to probes connector of the timer The transducers are