METHOD AND INSTRUMENT FOR COMBINATION WEIGHING

PROBLEM TO BE SOLVED: To adopt a first-in and first-out method, and to take a balance between a return rate and a marginal weight into account, in a combination weighing system. SOLUTION: In this combination weighing method wherein a reference cup filled at first out of cups joined in combination weighing is brought into a prescribed weight by collecting a plurality of blocks of food materials used with priority, the return rate Re is measured based on a working condition, and an LL value (a lower limit value of a weighing-objective range set initially), a UL value (an upper limit value of the weighing-objective range set initially), and a UUL value (a weighing relaxization value allowed as a limit value when the return rate is too high) are controlled based on change of the Re. A mean weight Ω of one piece in the fed materials and a standard deviation δ value thereof are measured based on the working condition, and the optimum combination of the LL, UL and UUL optimal to bring the combination weight W and the return rate Re within a terget value is read to be controlled.