Proper control of grinding circuits is essential for realizing the recovery and throughput goals of a beneficiation plant. Currently, control is determined by the availability, accuracy, and responsiveness of key measurements. Ideally, the real-time measurement of the particle size reporting to the overflow would be used to control the particle size produced by the grind circuit. Until a few years ago, this measurement was not available in real time with sufficient reliability for control systems, therefore surrogates, cyclone feed density or pressure or both, were used. The introduction of the impact-based particle size measurement method four years ago changed the situation and the ability of the industry to control their grind circuits. The results of testing the performance of this measurement technique at ten beneficiation plants and correlation with plant conditions reveal the inadequacy of controls based on pressure or density, and the need for direct control based on particle size. The principle of operation of this sampler-free measurement technology, its implementation, and measurement performance will be discussed. The control methods that are enabled by this unique system for both individual cyclone and battery level control will be illustrated.