Specifications

METTLER TOLEDO Weigh Module Systems Handbook
(12/99)3-4
Determining System
Accuracy and Repeatability
Experience has shown that a tank scale fully supported by weigh modules on a firm
foundation can be accurate to within 0.1% of the applied load (the weight placed on the
scale). When this type of scale is calibrated correctly, it will give an accurate reading of the
weight placed on it. Ideally, the percentage of total weight capacity should equal the
percentage of total counts (increments). This relationship is illustrated in Figure 3-1.
Counts
1,000
800
600
400
200
0
Half Load
(50% Capacity)
Full Load
(100% Capacity)
Perfect Performance
Ideal
Figure 3-1: Ideal Weight Capacity vs. Counts
If a scale has 1,000 counts and a total capacity of 5,000 pounds, then each count
should equal 5 pounds. When a 2,500 pound weight is placed on the scale, there
should be 500 counts. With a 5,000 pound weight, there should be 1,000 counts. This
relationship should not change regardless of whether weight is being added to or
removed from the scale.
When a scale is not calibrated correctly, this ideal relationship does not hold true. There
are four types of errors that cause inaccurate weighing:
• Calibration Errors
• Linearity Errors
• Hysteresis Errors
• Repeatability Errors