Abstract: An apparatus 400 and a method are provided for increasing the density of a compactible material 10 while continuously evaluating the density of the material. The evaluation of material density is carried out by calculating the total of the static, dynamic and centrifugal forces applied by a vibrating tool 102 l to the compactible material 10. The total applied force calculation includes measuring the vertical acceleration of the material contacting member 102 and the position of an eccentric mass 206 mounted on the material contacting member 102. The acquisition of these parameters is carried out simultaneously, and the calculation of the dynamic and centrifugal forces is made when the material contacting member 102 is at its lowest position.

Abstract: An apparatus and a method are provided for controlling the frequency of vibration of a compacting machine. The frequency control is carried out by the apparatus which determines the actual time at which a ground contacting member of the compacting machine is at its true vertically lowest position. This is determined by measuring the time at which the vertical acceleration of the ground contacting member has a maximum value during one rotation of an eccentrically mounted, vibration inducing mass. The time difference between the time at which the vibration inducing eccentric mass is at predetermined position and the time at which the acceleration of the ground contacting member is at the maximum value is used to calculate a phase angle relationship (.phi.) between the ground contacting member and the eccentrically attached member. This method of determining the phase angle relationship (.phi.