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Chapter 3: General Considerations

Weighing System Performance

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Weighing System

Performance

Accuracy, resolution, and repeatability are basic concepts used to measure a weighing

system’s performance.

Accuracy is how close the reading on a scale’s indicator is to the actual weight placed

on the scale. A scale’s accuracy is usually measured against a recognized standard,

such as NIST Certified Test Weights.

Resolution is the smallest weight change that a digital scale can detect. Resolution is

measured in increment size, which is determined by the capabilities of the load cells

and digital indicator. A digital weight indicator may be able to display a very small

increment size, such as 0.01 kg (resolution); however, that does not mean the system

is accurate to 0.01 kg.

Repeatability is a scale’s ability to display a consistent weight reading each time the

same weight is placed on the scale. It is especially important for batching and filling

applications, which require that the same amount of a material be used for each batch.

Repeatability and accuracy go hand in hand. You can have a repeatable system that is

not accurate, but you cannot have an accurate system unless it is repeatable.

The following factors can influence the accuracy and repeatability of a weighing system.

They are discussed in detail later in this handbook.

• Environmental Factors: Wind, Seismic Forces, Temperature, Vibration

• Weigh Module System Support Structures

• Tank and Vessel Design

• Piping Design (Dead-to-Live Connections)

• Load Cell Quality

• Total Load Cell Capacity

• Calibration

• Operational / Process Factors

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Mettler Toledo LJ16 Spezifikationen Seite 18