the last known flow rate after or in some cases during a detergent feed cycle the detergent flow rate is calculated and either the detergent feed time is modified for the current detergent feed cycle or it will be used for the next detergent feed time calculation this allows the controller to avoid any on off type proportioning and instead use derivative control to achieve the detergent concentration setpoint quickly and with minimal overshoot it also inherently gives the controller 12 the capability to optimize detergent feed for any of a variety of configurations and system lags without the need to predict them in advance this learning and comparing cycle is performed each time the controller 12 activates a solenoid valve 6 thus allowing a change to the controller 12 response function if and when conditions change such as water pressure or temperature the special challenges in the warewashing application require the controller 12 to make up wide differences between the actual detergent concentration 28 provided by the sensor 24 and set point as quickly as possible again without exceeding set point aggravating the process is a latency time between activating the detergent feed and reading the detergent concentration information 28 at the wash tank sensor 24 the detergent feed rate can vary greatly and must be compensated for the controller 12 first reads an interrupt condition 50 flag 3 flag 3 is an indication for the controller 12 to activate the solenoid valve 6.