Zero-adjustment in weighing apparatus

Claim 2

Zero-adjustment circuitry for use with a weighing machine adapted to provide an electrical output having a weight-indicating value which is a measure of the load weight carried by the machine, comprising: difference responsive means for producing from such an electrical output when the said load weight is zero a difference signal having a value which is a measure of the difference between the said weight-indicating value and a zero-point correction value which is initially of a preset magnitude; a comparator for comparing the value of the said difference signal with a reference signal value of a predetermined magnitude; and adjustment means for employing an output of the comparator to vary the said zero-point correction value so as to bring the value of the said difference signal towards equality with the said reference signal value.

Claim 5

The method according to claim 2, further including steps of: (a') converting said zero-point correction value into a digital value in the form of an m-bit binary number and producing a first digital value, in which solely the m-th bit is "1", as the initial zero-point correction value; (b') changing the (m-l)-th bit of said first digital value to "1" if the difference value between the initial zero-point correction value and the unloaded weight value is greater than the set value; (c') changing the m-th bit of said first digital value to "0" and the (m-l)-th bit thereof to "1" if said difference value is less than the set value; (d') finding a difference value between the unloaded weight value and an analog value obtained by applying a digital-to-analog conversion to a second digital value obtained from step (b') or step (c'); (e') changing the (m-2)-th bit of said second digital value to "1" if the last-mentioned difference value is greater than the set value; (f') changing the (m-l)-th bit of said second digital value to "0" and the (m-2)-th bit thereof to "1" if said last-mentioned difference value is less than the set value; (g') finding a difference value between the unloaded weight value and an analog value obtained by applying a digital-to-analog conversion to a third digital value obtained from step (e') or step (f'); (h') thereafter obtaining a zero-point correction value by sequentially executing processing for comparing subsequent difference values and the set value and for changing digital values based on said comparison operation.

Claim 8

The apparatus according to claim 4, wherein a plurality of said weighing machines are provided and arranged to construct a combinatorial weighing system, said means (a) through (e) performing a zero-point adjustment for all of said weighing machines.

Claim 9

The apparatus according to claim 4 or 5, wherein said control unit is adapted to store a difference value between a weight value from each weighing machine and a zero-point correction value for said each weighing machine, deliver the zero-point correction value for said each weighing machine when the weight value from the corresponding weighing machine is read, and obtain a true weight value by subtracting said stored difference value, which corresponds to said weighing machine, from the difference between said read weight value and zero-point adjustment value.