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Abstract

A detergent dispenser controller for use with a washing device, such as a dishwasher, that measures detergent concentration in a water tank by measuring the conductivity of the detergent solution in the water tank. The detergent controller automatically learns the feed rate of the detergent dispenser used, regardless of the type of detergent dispenser being used. For each detergent feed cycle, the controller computes a Feed Factor equal to the amount of detergent feed on time required for each unit increase in the detergent concentration, which is the inverse of the detergent feed rate. The controller stores the computed Feed Factor for the last N feed cycles in a non-volatile memory, and computes a running average of the N feed factors stored in the non-volatile memory. Whenever the detergent dispenser is powered on, it determines the difference between the measured wash tank detergent concentration and a specified detergent concentration set point value. The computed average feed factor and the difference between the set point and the current detergent concentration are multiplied to compute a detergent feed on time. The detergent dispenser is then turned on for the computed feed on time, and after a suitable subsequent mixing period, the change in detergent concentration during the last feed cycle is determined and a new Feed Factor is computed and stored. The detergent concentration is preferably measured using logarithmic measurement units, and separate Feed Factors may be computed and used for at least two detergent concentration ranges.

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