Sensor based variable rate application of crop inputs provides unique challenges for traditional rate controllers when compared to map based applications. The controller set point is typically changing every second whereas with a map based systems the set point changes much less frequently. As applied data files for a sensor based variable rate nitrogen applicator were obtained from a wheat field in north central Oklahoma. These data were analyzed to determine the magnitude and frequency of rate changes. A model based a commercially available rate controller was developed. Results from this model predicted a mean absolute application error of 12.9 L ha-1. This error could likely be reduced by half if the controller delay was reduced by 1 second.