What is external resolution?
External resolution, also called display resolution, is displayed in the weight window of the scale. It is calculated by dividing the capacity of the scale by the internal resolution. In most load cell-based counting scales, the external resolution will be one part in 10,000, or 1/10,000. Since calculations in a counting scale are made using internal resolution, external resolution is more important when manually or digitally introducing a tare weight. Less accurate counts result if the value of the tare container is rounded.
What is internal resolution?
The internal resolution of a counting scale is the number of divisions into which it divides the total capacity of the scale.
Example: A 50-pound counting scale with one million-count resolution divides the 50 pounds into 1,000,000 parts. This means each internal resolution is translated to 50/1,000,000 or 0.00005 pound.
All weights are calculated on this basis. For example, if some parts were placed on the counting scale, and the internal display showed 12,307 internal counts, the weight to be displayed would be 12,307 times 0.00005 pound = 0.61535 pound. Since the weight display might only be five digits, then the weight display would show as 0.615. This is the external resolution.
The operator then keys in the sample quantity; for example, 15 pieces. The scale still knows how many internal counts are being used (12,307) and now divides this number by 15 to get the number of internal counts per piece: 12,307 / 15 = 820.4666. The scale has to round off the number to get rid of the decimal, therefore, the scale calls each piece as 820 internal resolution counts. The scale will convert the piece weight into pounds by multiplying the weight per count times the number of counts: 0.00005 × 820=0.041. This is displayed in the unit, or piece-weight, window. When the scale detects a change in the weight, it will complete the calculation in reverse, using the number of internal resolutions per piece as the divisor. For example, more pieces are placed on the scale and the number of internal resolutions is now 346,712: 346,898 / 820 = 423.04, rounded to 423 pieces.