4-16 Packet Reference Manual
Sum of Products Calculation
This is an example of how the printer uses Sum of Products to calculate a check digit for this
data:
5 2 3 2 4 5 2 1 9
1. Weights are applied to each digit, starting with the last digit in the weight string. They are
applied right to left, beginning at the right-most position of the field. Remember, a weight
string must contain at least two different numbers. This example has a weight string of
1,2,3,4:
field: 5 2 3 2 4 5 2 1 9
weight string: 4 1 2 3 4 1 2 3 4
2. Each digit in the field is multiplied by the weight assigned to it:
field: 5 2 3 2 4 5 2 1 9
weight string: 4 1 2 3 4 1 2 3 4
products: 20 2 6 6 16 5 4 3 36
3. Next, the product of each digit is added together. This is the sum of the products.
20 + 2 + 6 + 6 + 16 + 5 + 4 + 3 + 36 = 98
4. Divide the sum of the products by the modulus (10 in this case), only to the whole number.
The balance is called the remainder.
9
10 98
90
8
5. Subtract the remainder from the modulus.
The result becomes the check digit. In this case, the check digit is 2.
10 - 8 = 2
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