Grading grains and other particulate materials - by applying vibration to obtain reproducible compacting and determining mass by natural frequency of vibration

摘要

The procedure improves the accuracy in grading grains and other particulate materials through a measurement of dielectric constant or induction coefficient in an A.C. electric field, which depend e.g. on water content or other constituents, but are also affected by the total mass and compacting density of the particles. The sample is to be compacted to a reproducible degree in the sample holder before the measurement, by applying a vibration, pref. ultrasonic, to the holder during or after loading. The sample mass can pref. be determined through the resonant frequency of the filled holder. After loading, the AC generator stops (22) and the holder (12) elastically mounted (21) continues to vibrate at the natural frequency of the system, where the sample mass is the only variable. The solenoid (19) generates a signal at this frequency and feeds it to the processur unit (18). The impedance is measured between the centre electrode (11) and the holder wall (10).