The scale is a device we encounter in our everyday lives that helps us measure weights. It is an indispensable tool in many areas, be it cooking, sending packages or industrial processes.
A scale is basically an instrument designed to measure the weight of an object. It usually consists of a platform or hanging device and a scale on which the weight can be read. By placing the object to be weighed on the platform or hanging it from the hanging device, the weight can be determined.
In the field of scales, however, there are different types and categories, which are differentiated according to the area of application and functionality. An important distinction in the industrial sector is that between non-automatic and automatic scales.
Non-automatic vs. automatic scales
A non-automatic weighing instrument (NAWI) – often referred to in the guidelines mentioned below in particular – is a type of weighing instrument that requires measurement by operators. A non-automatic weighing instrument has a scale or display on which the weight of the object to be weighed can be read. The use of NAWI is widespread in commerce, industry and other areas where precise measurements are required.
In contrast, there are self-acting scales that perform the weighing automatically. The process of weighing is always started by itself and consequently, self-acting scales play a crucial role in the automation of industrial production.
In the following, we will focus on non-automatic weighing instruments and the regulations that must be observed.
What is a verified or legal-for-trade scale?
A verified scale or trade approved scale is a non-automatic weighing instrument that has been subjected to verification and that complies with the legal requirements (in particular EU Directive 2014/31, EU Directive 2014/32 – also known as MID which are) in legal metrology, as well as being subject to regular inspection by the Weights and Measures Office.
The aim of verification is to protect the consumer and the public interest. Verification by an authorised body ensures that the scale provides accurate and reliable weight measurements and that verification error limits are observed. A verified scale is used in business areas where weight has legal relevance, such as in commerce, medicine or certain legal-for-trade activities.
From January 1, 2021, the European Union (Withdrawal) Act 2018 came into effect in the UK, incorporating EU-derived legislation, including product safety and metrology laws, into UK domestic law. The Product Safety and Metrology (Amendment etc.) (EU Exit) Regulations 2019 amended this retained legislation to address issues resulting from the UK’s departure from the EU and to provide specific provisions for the GB market.
Key points to note about these changes include:
- Safety and technical requirements for products have not changed.
- Products legally placed on the European Economic Area (EEA) or UK markets before January 1, 2021, can continue to circulate in the UK.
- CE marked products will continue to be accepted on the GB market until December 31, 2021. Additionally, the government intends to extend the recognition of the CE marking for most goods placed on the market in Great Britain indefinitely, beyond December 2024. These updates apply to 18 regulations under the Department for Business and Trade (DBT), covering various product categories, including non-automatic weighing instruments and measuring instruments.
- UK Notified Bodies automatically become UK approved bodies from January 1, 2021, for conformity assessment of products for the GB market.
How do you recognise a verified scale?
In the UK, markings on a non-automatic weighing instrument are important for ensuring accurate and transparent measurement. These markings help consumers and businesses alike to understand the instrument’s specifications and compliance with regulatory standards. Here are the key markings that you may find on a non-automatic weighing instrument in the UK:
- CE Mark: The CE mark indicates that the weighing instrument complies with European Union (EU) regulations and meets the necessary safety and performance standards.
- UKCA (UK Conformity Assessed) Mark: The UKCA marking consists of the letters “UKCA” in capital letters, often displayed in a circle, similar in appearance to the CE mark. The symbol should be easily visible on the product, its packaging, or an accompanying document. It is used to demonstrate that the product conforms to UK regulations and standards, replacing the CE mark for products sold in Great Britain (England, Scotland, and Wales) after Brexit.
- UKNI Mark: The UKNI marking is a new conformity mark for products sold in Northern Ireland. It’s used for goods that have been checked by a UK-based organization to make sure they meet the rules. This guide will show you how to use the UKNI marking, which is sometimes called the UK(NI) mark or the UK(NI) indication.
- The M Marking: The M sticker tells you that the equipment it’s on has been made to meet the legal rules for measurements. You can also see the year it was made next to the M, but only on newer equipment. For older equipment, the year is next to the CE mark.
| Goods on the market in Great Britain | Accepted markings |
| For products manufactured and placed on GB market until 31 December 2024 | CE or UKCA |
| For products manufactured and placed on GB market until 31 December 2024 | UKCA |
Additionally, if you are placing qualifying Northern Ireland goods on the market in Great Britain under unfettered access, the acceptable markings or combination of markings are as follows:
| For qualifying Northern Ireland products being placed on the GB market under unfettered access | CE or combination of CE and UKNI mark |
Sealing switch for industrial weighing systems: Important function for verification and safety
The seal switch plays a crucial role in the verification and security of scales, especially in commercial and industrial environments. This special switch, often referred to as a seal switch, is an essential element that ensures the integrity and compliance of a calibrated scale.
What is a seal switch?
The seal switch is a safety mechanism that is built into many scales. It is used to control and secure access to the calibration and adjustment settings of the scale. After Verification, the seal switch is sealed to prevent unauthorised or unintentional changes to the scale settings. This ensures that the scale continues to comply with legal requirements and calibration standards.
Handling the sealing switch
- Verification and sealing: After a scale has been verified, the sealing switch is sealed by an authorised verification body. This is to ensure that the settings of the scale have not been changed since the last verification.
- Maintenance and repair: If a scale requires maintenance or repair, it may be necessary to remove the seal. In this case, the scale must be re-verified and the sealing switch resealed to ensure conformity with legal requirements.
The different accuracy classes of non-automatic weighing instruments
In the EU Directive 2014/31, so-called accuracy classes are defined, which indicate how precise a scale is when weighing objects.
These accuracy classes can be represented in different mass and weight units (according to Directive 80/181/EEC of 1979). The following mass and weight units are permitted:
- SI units: Kilogram, microgram, milligram, gram and tonne.
- British units: Troy ounce (when weighing precious metals).
- Other units: Carat (when weighing precious stones).
Accuracy classes contribute to the categorisation of scales in many ways:
- They are used to determine the suitability of the balance for certain applications.
- They define the tolerance limits that are applied when testing the balance.
For a scale to be assigned to a specific accuracy class, it must meet certain criteria. Classification is based on two aspects:
- The number of verification scale intervals(n): This refers to the ratio of the capacity of the scale to its smallest representable unit, i.e. resolution, and is also simply called division. However, in EU Directive 2014/31, the legislator speaks of the number of verification scale intervals (n).
- The verification scale interval (e): This is the smallest weight interval that can be used in weight-based price determination with a particular scale in a trading context.
What is the verification scale interval (e)?
For non-automatic weighing instruments, the verification scale interval (e) refers to the smallest legally approved and technically possible scale interval. In other words, it determines the smallest weight that the scale can reliably measure.
The verification scale interval (e) is given in the same unit of measurement as the weight value (for example, grams, kilograms, i.e. the SI units mentioned above). A scale with a verification scale interval (e) of 1 gram would, for example, round weights to the nearest whole gram. A scale with a calibration value of 0.01 grams, on the other hand, could measure weights to the nearest hundredth of a gram.
Accuracy classes: A decisive categorisation for non-automatic weighing instruments
The following accuracy classes – related to the verification scale interval (e) – have been defined by the legislator depending on the requirements and intended use of the scale:
- Class I: Precision scales. These scales are particularly precise and are suitable for accurate measurements in laboratories or special applications. The verification scale interval (e), i.e. the smallest unit of weight that the balance can measure, is at least 0.001 grams. This includes our analytical balances!
- Class II: Precision Balances. These scales have a slightly lower accuracy than class I, but are still precise. The verification scale interval (e) can be between 0.001 gram and 0.05 gram. Take a look at our selection of precision scales here!
- Class III: Commercial scales. These scales are used in commercial environments such as shops or supermarkets. They are less precise than class II, but still sufficiently accurate for commercial use. The verification scale interval (e) can be between 0.1 gram and 2 gram.
- Class IIII: Coarse scales. These scales are used for coarse measurements where high accuracy is not required. The verification scale interval (e) is at least 5 grams.
The following table shows the accuracy classes with the number of scale intervals (n) and the verification scale interval (e).
| Accuracy classes according to EU Directive 2014/31 | |||||
|---|---|---|---|---|---|
| Class | Verification scale interval (e) = Smallest weight that the scale can measure | Minimum load (min) | n = ((Max)/(e)) = Capacity / Readability | Application | |
| Minimum value | Minimum value | Maximum value | |||
| I | 0,001 g ≤ e Simply put: ≥1 mg | 100e | 50 000 | – | High-precision weighing in laboratories |
| II | 0,001 g ≤ e ≤ 0,05 g Simply put: 1 to 50 mg | 20e | 100 | 100 000 | Laboratory weighing for products such as gemstones and metals or crops |
| 0,1 g ≤ e Simply put: ≥100 mg | 50e | 5 000 | 100 000 | ||
| III | 0,1 g ≤ e ≤ 2 g Simply put: 0,1 to 2 g | 20e | 100 | 10 000 | Commercial weighing of products such as precious metals and semi-precious stones. Also used for weighing animals, laundry, mail and vehicles |
| 5 g ≤ e Simply put: ≥5 g | 20e | 500 | 10 000 | Commercial weighing for heavier loads, e.g. livestock, vehicle scales with a higher capacity. | |
| IV | 5 g ≤ e Simply put: ≥5 g | 10e | 100 | 1 000 | Weight checks in road traffic, e.g. wheel load scales |
The accuracy classes illustrated with an example
Accuracy class I
Analytical balances are a special type of balance usually used in laboratories or medical facilities. It is used to measure the mass or weight of substances or objects with high accuracy. Analytical balances are designed to take very precise measurements and can often be accurate to several decimal places.
With our Gram FV analytical balance, you can choose a maximum weighing range of 120 grams with a readability of 0.0001 grams.
If we want to calculate the number of scale intervals (n), then the weighing range of 120 grams here corresponds to the capacity and the readability remains at 0.0001 grams.
With the formula n = ((Max)/(e)) = 120/0.0001 we get the result of 1 200 000. Thus this scale belongs to accuracy class 1.
Accuracy class II
A precision balance is a measuring instrument used to measure the weight or mass of an object or substance with high accuracy. Precision scales are often used in laboratories and industrial environments where accurate measurements are critical.
With our Gram FR precision scale, you can choose a maximum weighing range of 500 grams with a readability of 0.001 grams.
Using the formula n = ((Max)/(e)) = 500/0.001, we get the result of 500.00. Thus, this scale belongs to accuracy class 2.
When do verified scales have to be used?
Directive 2009/23/EU on non-automatic weighing instruments states that verified instruments must be used in the following circumstances:
- Determination of mass for the purposes of commercial transactions,
- Determination of quantity for the calculation of a toll, tariff, tax, bonus, penalty, allowance, compensation or similar type of payment.
- Determination of quantity for the application of laws or regulations; expert evidence in legal proceedings.
- Determination of price on the basis of quantity for the purposes of direct sale to the public and the assembling of prepackages.
- Determination of mass in the practice of medicine when weighing patients for the purposes of medical supervision, examination and treatment.
- Determination of quantity in the practice of medicine for weighing patients for the purposes of monitoring, diagnosis and medical treatment.
- Determination of quantity for the preparation of medicines on prescription in a pharmacy and determination of quantity in analyses in medical and pharmaceutical laboratories.
What is the difference between a Verified scale, verifiable scale and a non-verifiable scale?
A verified scale, a verifiable scale and a non-verifiable scale differ in terms of their verifiability and their usability in commercial transactions.
- Verified scale: A verified scale is a scale that has been subjected to verification and bears a valid verification mark or a verification symbol. Verification is carried out by officially recognised verification bodies and ensures that the scale meets the legal requirements for accuracy and reliability. Verified scales are regularly checked and adjusted to ensure their accuracy. They are used in commercial transactions where weights are required by law to ensure the integrity and trustworthiness of the measurements.
- Verifiable scales: These are scales that meet the basic requirements for subsequent verification. These scales must meet certain technical standards and can be verified later to confirm their accuracy. Verifiable scales are often used in industrial or manufacturing environments where weight is important but not legally binding. As a result, a verifiable scale is not verified by the manufacturer. However, it is possible to have the scale verified at the responsible weights and measures office.
- Non-verifiable scales: A non-verifiable scale is a scale that is not suitable for use in commercial transactions because it does not meet the legal requirements for accuracy and reliability.They are not subject to regular verification and may not be used for commercial transactions where weights are legally required. Non-verifiable scales can weigh as accurately or even more accurately than verified scales, provided they are regularly maintained and adjusted. However, from a legal point of view, they can never be subjected to verification and consequently can never be classified as “legal for trade” scales.
What is the difference between factory calibration, calibration, configuration and verification of a weighing instrument?
The terms calibration, adjustment and verification all refer to measures taken to ensure the accuracy and reliability of measuring instruments such as scales.
1. Factory calibration
Factory calibration is a calibration performed by the manufacturer before the scale is used for the first time. During factory calibration, the scale is set to give accurate measurements in the specified environment. Factory calibration is usually performed with high-precision reference weights and allows the manufacturer to ensure that the scale meets specified accuracy standards before it is shipped to the customer.
2. Calibration of a scale
Calibration refers to the process of checking the measurement accuracy of an instrument and adjusting it when necessary. This is usually done in-house or by a specialised company. The measuring instrument is compared with a known reference to determine whether it provides correct readings. If deviations are found, appropriate corrections are made to improve accuracy. Calibration can be performed, for example, by comparing a scale with standardised weights.
How does the calibration of a scale work?
The calibration process starts with the definition of the measurement process, including the instrument, the environmental conditions, the standards used and the procedure. Using a mathematical model, the calibration is carried out taking into account all known influences (temperature, chemicals, wear). This is followed by an analysis of the measurement uncertainty. The results, including the calibration value and the calibration uncertainty, are documented.
The procedure of a scale calibration includes placing calibration weights on the scale and determining the deviation based on the displayed weight values. The measurements are performed several times during calibration and statistically evaluated. Alternatively, fixed standard test conditions can be used to minimise random deviations.
The result of each measurement is recorded as the deviation between the total value of the reference weights (X) and the value displayed by the scale (Y). This deviation is called an error and is documented in the calibration certificate.
Our ISOCAL calibration certificates contain information about the calibration process carried out and the procedures and results used. Your scale is subjected to a repeatability test, an eccentricity test and a charge and discharge test. Furthermore, our ISOCAL calibration certificates contain a complete report on the measurement standards used.
3. Configuration of a scale
Adjustment or Configuration refers to the process of fine-tuning or adjusting a scale to optimise accuracy. After calibration, minor deviations or inaccuracies can be corrected by configuration. This can be done, for example, by adjusting the mechanical or electronic components of a scale to make the readings more accurate. While a calibration is carried out by trained personnel, a configuration can easily be carried out at home. There are several ways to adjust your scale:
- Configuration with calibration weights: Most scales can be adjusted with a special calibration weight. Follow the instructions in the user manual of your scale. The calibration weight is placed on the scale and the scale display is then adjusted accordingly.
- Configuration with an already calibrated scale: If you have a second scale available that is correctly adjusted, you can use it to measure the weight of an object, which you then use as a calibration weight for the scale to be adjusted. Measure the weight of the object with the correctly calibrated scale and then use this weight to calibrate the other scale.
4. Verification of a weighing instrument (conformity assessment)
Verification is a legally regulated procedure in which a measuring device, e.g. a scale, is tested, validated and given a verification mark by a state-approved verification authority. Verification confirms that the device meets the legal requirements for accuracy and reliability. It includes both the verification and the adjustment of the device. Verified scales are regularly reverified to ensure that they continue to provide correct measurement results.
| Factory Calibration | Calibration | Configuration | Verification | |
| Regulation | No statutory regulation | No statutory regulation | No statutory regulation | Legal regulation according to EU Directive 2014/31 |
| Purpose | Inspection of the equipment, recommissioning of the equipment after a longer break, general control of the equipment | Ensuring the accuracy of a measuring instrument, especially in the context of a quality management system | Fine-tuning a measuring instrument to improve accuracy, usually after calibration. | Required by law if you participate in so-called “legal metrology”. In short: in commercial transactions, e.g. determination of price on the basis of mass in supermarkets. |
| Application | Required by law if you participate in so-called “legal metrology”. In short: in commercial transactions, e.g. determination of price on the basis of mass in supermarkets. | Any scale that functions faultlessly | Any measuring instrument that requires fine-tuning to ensure optimum accuracy | Only legal-for-trade scales or checkweights that comply with the standards of the OIML |
| Procedure | No legal regulation, but factory calibration is usually carried out in the same way as calibration. Measurement deviations are recorded with the aid of calibrated weights. A factory calibration certificate is issued. | Comparison of the measuring instrument with a known standard; corrections are made if deviations are found | Adaptation of the mechanical or electronic components of a measuring instrument to improve the measuring accuracy | Verification and validation of a measuring instrument by a state-approved verification authority |
| Validity | Determined by the user in accordance with standards and regulations | Recognised through multilateral agreements between various international accreditation organisations | Depends on the accuracy of the instrument after adjustment | Certified by verification and required by law |
| Frequency | Can be carried out as required, e.g. when the scale is put back into operation after a long break. | Compliance with recalibration periods, usually 12 months | Perform as required when minor deviations or inaccuracies are detected | Depending on the legal requirements and regulations for the respective measuring instrument: Depending on the maximum load, type of scale and type of use, the calibration must be renewed annually, every 2 or 3 years. |
What other regulations must be complied with?
Overall, there are various guidelines for using non-automatic weighing instruments – i.e. weighing instruments that have to be used with human assistance – in a proper manner.
- Standards and directives of the Organisation Internationale de Métrologie Légale (OIML)
- Weights and Measurement Act 1985
FAQ’s – Frequently Asked Questions
Do scales need to be calibrated and if so, how often?
Calibration of a scale is generally recommended, even though there is no legal requirement to do so. However, correct and reliable weight measurement is an important prerequisite for productivity and efficiency.
If your company has implemented a quality management system such as ISO 9000ff, IATF 16949, GMPV, DA, GLP, FDA or similar, there is an obligation to calibrate measuring equipment, including scales. This obligation arises from the normative requirements of the quality management system.
What risks arise if a scale is not calibrated?
- Inaccuracy in weight measurement: A scale that is not calibrated may show incorrect weight values. This can lead to erroneous results, especially when it comes to precise weight measurements, such as in medical or scientific applications.
- Lack of reliability: An uncalibrated scale can be unreliable and lead to inconsistent measurements. This can lead to confusion or uncertainty about actual weight changes or values.
What are the risks when a scale is not verified?
- Legal consequences: In some areas, such as retail or certain weight regulations, regular verification is required by law. If a scale is not calibrated, there may be legal consequences such as fines or loss of licences.
How much does the verification of a scale cost?
Verification costs are incurred both for the initial verification by the manufacturer and for subsequent verifications by state verification offices. At Weighing-Net, all verification costs are included in the price if you purchase a verified scale.
What is levelling?
Levelling a scale refers to the process of balancing the scale to ensure it is in a horizontal and stable position. Levelling ensures that the scale gives correct measurements by making sure that the scale is not tilted and that the measuring platform is parallel to the floor. This can be achieved by adjusting the legs or using levelling feet. A correctly levelled scale ensures accurate and reliable measurement results.
Does a verified scale weigh more accurately than an unverified scale?
No, a verified scale does not weigh more accurately than an unverified scale. Verification of a scale only refers to the verification and confirmation of its accuracy by an authorised body. A verified scale ensures that it meets legal requirements, but this does not necessarily mean that it is more accurate than an unverified scale.
The accuracy of a scale depends on several factors, including the quality of the scale system, the calibration and the method of measurement. A good quality non-verified scale can be just as or even more accurate than a verified scale, as long as it is properly maintained and calibrated. It is important that scales are checked and maintained regularly, whether they are verified or not, to ensure accurate measurements.
Are all scales calibrated from the factory?
Usually all scales are calibrated from the factory. This means that they are tested and adjusted in a controlled environment by the manufacturer to ensure that they give accurate measurements. These scales should be able to give accurate measurements straight out of the box.
Are all scales factory verified?
No, not all scales are factory verified. While most scales are factory calibrated to ensure they give accurate measurements, verification is a separate process regulated by law.
