Calibration error limits and give-away: Overfilling as a cost factor in the filling process

In the industrial filling of bulk materials, measurement accuracy is crucial in determining how closely the actual fill volume matches the nominal fill volume. Any deviation directly affects the amount of product dispensed per unit.

The consequence is measurable: To ensure compliance with legal requirements, overfilling occurs systematically. This overfilling, also known as give-away, adds up to significant quantities at high throughput rates and thus incurs direct costs that are often not visible during ongoing operations. Key control variables are the accuracy class, the calibration error limit, and the actual process variation. These parameters determine the size of the necessary safety margin and how much product is actually wasted during the filling process.

The following article highlights the technical relationship between accuracy classes and calibration error limits, the impact of regulatory requirements such as the Prepackaged Goods Ordinance, and how concrete economic effects can be derived from these in industrial bulk filling.

Accuracy classes define the measurement resolution and the permissible deviation of a scale. As such, they directly determine the degree of variation in fill quantities relative to the nominal fill quantity in industrial bulk material filling.

In filling processes, the accuracy class is not a formal parameter, but rather the basis for the achievable dosing accuracy. It specifies the weight increments (calibration value), defines the permissible errors (calibration error limits), and determines the statistical variation of the fill quantities. This variation, in turn, determines the necessary safety margin and thus the give-away.

The accuracy classes under EU Directive 2014/31/EU differ in terms of their resolution and permissible error ranges, which are defined by the verification factor (e).

Class I: highest accuracy (laboratory applications, very small loads)
Class II: high accuracy (precision balances)
Class III: medium accuracy (commercial and industrial scales)
Class IIII: low accuracy (rough-use scales for large quantities of bulk materials such as sand or gravel)

In the industrial filling of bulk materials, Class III is the standard, as it ensures the necessary balance between measurement speed, robustness, and sufficient accuracy. The key parameter is the verification factor (e). It describes the smallest verifiable unit of weight and forms the basis for all other parameters:

Resolution (d): Display interval of the scale
Maximum capacity (Max): Maximum load capacity
Minimum capacity (Min): Lower operating limit
Resolution (n = Max / e): Number of measurable intervals

The verification factor is directly linked to the verification error limit . The permissible deviation of a scale is defined in multiples of e. Thus, e determines both the display resolution and the maximum measurement uncertainty. The larger the verification factor, the greater the possible deviations per measurement. These deviations increase the variation in fill quantities. To avoid underfilling, the filling process must account for a larger safety margin, which increases the give-away.

For a 25-kg bag, this means specifically: A scale with e = 20 g produces a greater measurement uncertainty than a scale with e = 5 g. This difference directly affects the required overfill margin and thus the annual product loss.

The required accuracy class depends on whether the scale is operated statically (non-automatic) or as part of an automatic filling system.

Non-automatic scales are subject to Directive 2014/31/EU and are classified into Classes I–III. In automated filling systems, however, automatic scales are used, which are classified according to the MID Directive and use percentage error limits (for example, Class 0.5).

The following applies to industrial bulk material filling:

• Automatic filling scales typically operate in Class 0.5
• The error limit is defined as a percentage deviation from the measured value
• The resulting measurement uncertainty directly influences the variation in fill quantities

The key relationship remains the same:

• Higher resolution (smaller calibration value or stricter class)
• lower measurement uncertainty
• lower standard deviation of fill quantities
• smaller safety margin required

→ less give-away

This makes the accuracy class an economic control parameter. It not only defines the technical performance of the scale but also determines how efficiently a filling process can be operated in terms of material usage.

Calibration error limits define the maximum permissible measurement deviation of a scale and thus determine the uncertainty of each individual weighing operation in industrial bulk material filling.

While the accuracy class specifies the structural resolution, the calibration error limit determines the error actually permitted during operation. This deviation directly affects the variation in fill quantities and thus the required safety margin to prevent underfilling.

Calibration error limits are defined based on the calibration value (e) and the load range of a scale. A distinction is made between initial calibration and operation.

Calibration error limit (initial calibration): maximum permissible deviation during commissioning
Traffic error limit (during operation): maximum permissible deviation during use (usually twice as high as during initial calibration)

The error limit is always a multiple of the calibration value. This creates a direct relationship:

Calibration value (e) → Error limit → Measurement uncertainty → Variation → Give-away

For Class III scales, for example, the following typical ranges apply:

The traffic error limit is critical during operation, as it describes the actual measurement uncertainty of the filling system.

The Prepackaged Goods Ordinance stipulates that the nominal fill quantity must be met on average and that deviations in individual packages must remain within certain limits. This results in two key requirements for industrial bulk filling.

Average value requirement: The average fill quantity must not fall below the nominal fill quantity.
Individual value condition: Individual packages must not exceed the permissible negative deviation.

Inspection can be performed in two ways:

1. Measurement: Each package is weighed, but documentation is not mandatory.
2. Inspection: Random sampling with documentation and calculation of the average.

Additionally, the following applies to downstream checkweighers: The margin of error must not exceed 0.2 times the permissible negative deviation. This ensures that the measurement uncertainty of the inspection is not greater than the permissible tolerance.

Relation to filling practice:
Regulatory requirements define the lower limit (no underfilling), while the calibration error limit specifies the measurement uncertainty. Both inevitably result in a safety margin.

Calibration error limit + process variation → necessary offset → give-away

This makes the Prepackaged Goods Ordinance an indirect cost driver: Although it does not force the filling process to overfill, it makes overfilling unavoidable if measurement accuracy is insufficient. The more precise the weighing technology is and the lower the variation, the smaller this safety margin can be—and the more efficiently the entire filling system operates.

"Give-away" refers to the systematic overfilling beyond the nominal fill volume. In industrial bulk filling, this represents a direct product loss that is often underestimated. Unlike scrap or dust losses, give-away is not a visible defect, but rather a deliberately planned safety margin. It arises from the combination of measurement uncertainty (calibration error limit) and process variation and is necessary to reliably comply with regulatory requirements.

The term “give-away” refers to the difference between the actual fill volume and the nominal fill volume. It is a necessary safety margin designed to prevent underfilling. The chain of causes can be clearly derived from a technical perspective: The overall variation in fill quantities results from the statistical superposition of measurement uncertainty (calibration value, calibration error limit) and process-related variation (dosing, material flow).

This variation is described statistically, typically using the standard deviation. The greater the variation, the further the target quantity must exceed the nominal fill quantity to ensure that no package falls below the permissible negative deviation.

Logic of filling practice:

Large variation → large safety margin
Small variation → small safety margin

The safety margin is nothing other than give-away. This results in the following direct relationship:

Calibration value + calibration error limit + dosing behavior → variation → safety margin → give-away

In industrial bulk filling, give-away is therefore not a random variable, but a process-related parameter that depends on the quality of the measurement technology and the stability of the filling process.

The costs associated with giveaways are calculated directly by multiplying the overfill amount per unit by the total throughput and the product value.

Specific example:

Bag weight: 25 kg
Throughput: 200 bags per hour
Operating time: 8 hours per day
Production days: 250 days per year
Annual volume: 400,000 bags

With an average give-away of 50 g per bag, this results in:
0.05 kg × 400,000 bags = 20,000 kg per year

At a product price of €2/kg:
20,000 kg × €2 = €40,000 per year

These costs arise without any visible loss process being apparent: The product is delivered as usual, but not paid for.

Scaling effect:

Higher throughput → proportionally higher loss
Higher product value → proportionally increasing cost impact

For high-priced bulk goods, such as fine chemicals or additives, the same mechanism can lead to losses in the six-figure range per year.

Context within the process:

Give-away is therefore not a side effect, but a key economic indicator for the filling plant. It describes how efficiently the combination of weighing technology, dosing, and process control actually works. Or, to put it technically: Give-away is the result of the difference between the regulatory minimum quantity and the precision achievable under process conditions.

This makes give-away a process-oriented metric that allows the efficiency of the filling plant to be measured directly, as illustrated by this classification of give-away as a process-oriented metric in filling operations.

The give-away can be reduced by systematically minimizing the variation in fill quantities through more precise weighing control and controlled dosing. It is crucial to minimize both measurement uncertainty and process-related fluctuations simultaneously. Only when both factors are consistently controlled can the safety margin be reduced without increasing the risk of underfilling.

Modern weighing control systems reduce variations in fill quantities through high-resolution measurement and adaptive control of the dosing process.

The core principle is multi-stage dosing:

Coarse dosing: rapid material feed until close to the target value
Medium dosing: reduced feed rate to approach the target
Fine dosing: precise attainment of the target weight

The key factor is post-flow correction: When the material flow is shut off, the product continues to fall freely. Modern systems calculate this residual quantity in real time and deliberately stop the inflow before the target weight is reached. This creates the following relationship:

Measurement resolution + real-time control → precise shut-off point → lower variation → less give-away

Technically, this is made possible by:

high-resolution A/D conversion (e.g., 24-bit)
high sampling rates (e.g., ~110 Hz)
internal resolution in the range of up to 200,000 d (with a display that is also calibratable)

This combination enables real-time processing of weight signals and dynamic adjustment of the dosing process—as is also implemented in modern systems such as the VeloScale weighing control.

Alibi memory and fill curves additionally enable seamless documentation of the filling processes. This not only meets regulatory requirements but also makes process deviations visible and allows for targeted optimization. Here are further details on measurement resolution and real-time control in modern systems: VeloScale weighing control for precise filling results

Filling accuracy is determined not only by the scale, but also by the interaction between the weighing control system and the dosing mechanism. While the scale measures, the dosing mechanism determines how the material is controlled as it enters the container. An uneven or difficult-to-control material flow increases variation and thus the required tolerance range.

Typical dosing principles:

Pneumatic dosing: fine control via air flows, suitable for powdered products
Turbine dosing: mechanical transport, high performance with free-flowing granules
Screw dosing: continuous material flow, easily controllable with certain bulk materials

Another influencing factor is the airflow within the system. Uncontrolled air movements can alter the material flow and increase the variation in fill quantities. This is where vacuum methods come into play. Targeted airflow stabilizes the material stream, thereby improving the reproducibility of the dosing. It turns out that the vacuum process not only affects dust-free bagging but also improves dosing accuracy—as seen with the VeloVac vacuum process or the BVP and BVT dosing systems.

Relation to filling accuracy:

Dosing mechanism + air guidance → material flow stability → lower variation → less give-away

The accuracy of the filling system has a direct impact on the total cost of ownership (TCO), as it determines both systematic product loss due to give-away and process stability. While the investment costs are a one-time expense, deviations in filling accuracy have a continuous impact on ongoing operations. Any reduction in variation permanently lowers the amount of product dispensed per unit—and thus the total costs over the system’s lifetime. Less give-away reduces material consumption per filled unit.

The savings result from:

Reduction in overfill amount × throughput × operating time × product price

This makes measurement accuracy a linear cost lever that increases in effect as production volume rises.

Compliance assurance:

Lower variation reduces the risk of underfilling. This decreases the likelihood of:

• Complaints from calibration authorities
• Customer complaints
• Follow-up inspections and process interruptions

The Prepackaged Goods Ordinance is not only formally complied with, but also consistently ensured within the process.

Process stability:

Consistent fill volumes increase the repeatability of the filling system. This leads to:

• fewer manual corrections
• more stable process parameters
• more predictable production

The filling system operates closer to its optimal operating point, without additional safety margins. Filling accuracy is thus a central component of the filling system’s total cost of ownership. Further information on the overall economic assessment can be found here: the total cost of ownership of the filling system over its lifecycle.

Integration into the overall process:

Filling accuracy directly influences the quality rate within Overall Equipment Effectiveness (OEE) and thus the actual usable production output. Lower variation increases the proportion of correctly filled units without rework or scrap. More detailed information on this can be found here: the quality rate within the OEE of a filling system.

Long-term perspective:

The economic evaluation of a filling system must not be limited to investment costs. What matters is the sum of all ongoing effects over the entire service life. These include:

• Material efficiency (give-away)
• Process reliability (compliance)
• Production stability (repeatability)

These factors determine the actual operating costs and thus the economic efficiency of the system.

In industrial bulk filling, measurement accuracy determines how much product is systematically dispensed in excess of the nominal fill quantity. Accuracy classes, calibration error limits, and process variation directly affect the required safety margin and thus the give-away. The more precise the weighing technology and the more stable the dosing, the lower the variation in fill quantities and the closer the filling can be operated to the nominal fill quantity. This reduces material losses while ensuring compliance with regulatory requirements.

Selecting the correct accuracy class and designing the weighing control system are therefore not purely technical decisions, but significantly influence the cost-effectiveness of the entire filling process. Our practical experience shows: Those who keep variation under control measurably reduce give-away and sustainably increase the efficiency of the filling system.