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What is a scale or weighing instrument?

Means a measuring instrument serving to determine the mass of a body by using the action of gravity on that body. A weighing instrument may also serve to determine other mass-related magnitudes, quantities, parameters or characteristics. (DIRECTIVE 2014/31/EU OF THE EUROPEAN PARLIAMENT AND OF THE COUNCIL of 26 February 2014)

What is a weighbridge?

Weighing instrument specially designed scale for weighing trucks.

What is a dynamometer or crane scale?

A dynamometer or Crane Balance is any graduated apparatus in order to indicate the strength of the force applied at one of its ends. Internally, most of the dynamometers are equipped with a mechanical system or load cells that distend as a force is applied, and in this way, they can measure the weight of a certain load.

What is a load cell?

Force transducer which, after taking into account the effects of the acceleration of gravity and air buoyancy at the location of its use, measures mass by converting the measured quantity (mass) into another measured quantity (output). (EN 45501:2015)

When we buy a scale, what should we consider?

Define how the equipment will be used (legal metrology or internal control), whether it will operate in a humid, corrosive or explosive environment, the maximum weighing capacity, the required accuracy, what information you need regarding weighing and how you want to save it.

Legal metrology or internal control?

Within the EU, and depending on the intended use, the weighing instrument must comply with legal and regulatory requirements established or not. Weighing instruments are products subject to CE marking of the manufacturer’s full responsibility. In the field of legal metrology, scales comply with one or more conformity assessment procedures of one or more European Parliament and of the Council directives applicable to them. For more information on the CE marking see the European Union website:

Weighing instruments which are intended solely for use in the internal checks of goods by the customer do not need the conformity assessment and respective EU Declaration of Conformity in accordance with Directive 2014/31 / EU.

What is Mandatory Periodic Verification?

Subsequent verification of a measuring instrument, carried out periodically at specified intervals according to the procedure laid down by the regulations. (OIML V 1:2013)

In Portugal, the legislation establishes the mandatory annual periodicity for carrying out the Periodic Verification of weighing instruments.

How to do the Periodic Verification of weighing instrument?

“Operation that, under specified conditions, in a first step, establishes a relation between the quantity values with measurement uncertainties provided by measurement standards and corresponding indications with associated measurement uncertainties and, in a second step, uses this information to establish a relation for obtaining a measurement result from an indication
Note 1 A calibration may be expressed by a statement, calibration function, calibration diagram, calibration curve, or calibration table. In some cases, it may consist of an additive or multiplicative correction of the indication with associated measurement uncertainty.
Note 2 Calibration should not be confused with adjustment of a measuring system, often mistakenly called “self-calibration”, nor with verification of calibration.
Note 3 Often, the first step alone in the above definition is perceived as being calibration. (OIML V 1:2013)”

Conformity Assessment or Instrument Calibration?

Depending on the intended use, the weighing instrument may be subject to conformity assessment and subsequent Periodic Verification (Legal Metrology) or Calibration in accordance with specific regulations requiring the calibration certificate as a means of periodic control.

Which entities are responsible for the legal metrological control of weighing instruments in service?

This regulatory discipline is the responsibility of the Instituto Português da Qualidade – IPQ (Portuguese Institute for Quality), that is a public institute, under the Ministry of Economy. The mandatory periodic reverification system is carried out by the Metrological Verification Bodies and 89 local authorities.

How important is calibration?

The most common way to characterize and evaluate the performance of a measuring equipment is calibration.

The calibration must be performed periodically and is the necessary condition for the measurement results to be considered reliable.

The result of a calibration must be presented in a technical document, called a calibration certificate. A certificate must provide various information on the calibration procedure and conditions. With this information it is possible to evaluate the performance of the equipment, comparing it with specifications of a certain standard, the manufacturer, or according to the tolerance of the process.

Is a weighing instrument subject to Conformity Assessment exempted from periodic verification in the following year?

Each EU country that establishes the legislation and regulations applicable to the in-service control of weighing instruments. In Portugal no, non-automatic weighing instruments are exempt from Periodic Verification until 31 December of the year in which it is submitted to one of the conformity assessment procedures provided for in Decree-Law No. 43/2017 of 18 April, as provided for in paragraph 2 of article 6 of Ordinance No. 320/2019 of 19 September

What are the advantages of the presence of the manufacturer during the execution of metrological control operations?

The manufacturer may make minor repairs or adjustments to the instrument, preventing it from being rejected during verification. It should be noted that if the instrument is rejected it can not be used until it has been repaired and re-metrologically verified.

I have a weighing instrument inserted into the production system, which controls do I have to perform?

In the control of the production process, and to eliminate losses or potential losses, the scales should be calibrated on a regular basis. If the company has a certified quality system (ISO 9001, ISO 14001, etc.) and uses the weighing instruments, in internal control of the production process, these must be submitted to an accredited calibration, whose certificates ensure the traceability of measurements to the International System (SI).

Why is it important to carry out preventive maintenance?

Although the advantages of preventive maintenance are recognized, at the moment of decision managers still see it as an unnecessary additional cost, resulting in later costs – in most cases, avoidable – with corrective maintenance that have negative impacts on their customers.

What are the gains with weighing systems in perfect condition?

Maintaining an efficient weighing system within the specified tolerances may appear to be costly and should be performed only when faults occur. However, when in perfect working condition, the weighing system can bring annual gains of up to 30%, preventing incorrect weighing of materials, for example.

In addition to the financial gains, it is also possible to point out the reduction of risks to the health and safety of clients and employees. When weighing in health areas, the dosage of a composite materials should be as accurate as possible, since the fractions of grams make the difference.

The control and monitoring of the weighing equipment, through the preventive and corrective maintenance, guarantees the perfect state of operation of the system, bringing economy, safety and tranquility.

Why you should to activate a maintenance contract? What are the advantages?

A maintenance contract allows to take advantage of a priority service, besides being able to schedule maintenance without needing to interrupt the production process due to the need for curative interventions. There are a number of advantages of a maintenance contract which, in addition to enjoying special discounts on the parts applied, can allow the intervention costs to be controlled.

What is the MID Directive?

The MID Directive (Measuring Instruments Directive) is a directive applicable to measuring instruments (DIRECTIVE 2014/32 / EU OF THE EUROPEAN PARLIAMENT AND OF THE COUNCIL of 26 February 2014) on the harmonisation of the laws of the Member States relating to the making available on the market of measuring instruments, that in the scope of application includes automatic weighing instruments (MI-006).

What is the effect of applying the EU directives to the end user?

With regard to the end user, the effects are evident, greater protection as a consumer, greater transparency in commercial transactions.

What is the conformity marking that a weighing instrument must have?

The conformity marking of a weighing instrument, in the terms of the Directives 2014/31/EU and 2014/32/EU, corresponds to the CE marking and supplementary metrology marking. The CE marking shall be subject to the general principles set out in Article 30 of Regulation (EC) No 765/2008 and the supplementary metrology marking shall consist of the capital letter ‘M’ and the last two digits of the year of its affixing, surrounded by a rectangle. The height of the rectangle shall be equal to the height of the CE marking.