HANDLING AND SPREADING OF FERTILIZERS .3. MEASUREMENT OF PARTICLE VELOCITIES AND DIRECTIONS WITH ULTRASONIC TRANSDUCERS, THEORY, MEASUREMENT SYSTEM, AND EXPERIMENTAL ARRANGEMENTS

A new technique for measuring the velocity and direction of fertilizer particles discharged by a fertilizer distributor is discussed. The technique is based on the Doppler frequency shift of an ultrasonic beam. The instantaneous amplitude and frequency of the received Doppler signals are computed by digital signal processing. The velocity and the direction of each detected particle are calculated from the instantaneous frequency and the particle diameter is estimated from the instantaneous amplitude. The technique is used to quantify the influence of physical properties of fertilizer on the motion of fertilizer particles in the distributor device. A first series of experiments shows that this technique can measure the velocity and direction of fertilizer particles. The estimation of the particle diameter is more difficult because of the non-uniform frequency response of the ultrasonic transducers in the frequency band used. © 1994 Silsoe Research Institute.