A calibrated scale must be used whenever the weight is used to determine a price. In addition, there are other applications that require a calibrated scale.
In our blog we have covered this topic in great detail and from the table you can easily determine whether your application requires a calibrated scale..
Legal basis - Directive 2014/31/EU
Directive 2014/31/EU deals with non-self-employment scales. In addition to these, there are the self-active scales, which we will deal with elsewhere. Crucially, this directive is binding on all scales and not just on calibrated scales. This is apparent directly from Article 1, paragraph 1. In paragraph 2, a distinction is then made according to the areas of use, which later results in the different handling of calibrated scales and non-calibrated.
Article 2 contains the definitions. This also gives rise to the definition of a scale and that of a non-self-active scale. The latter requires the intervention of an operator, which is not required for an actuated scale. Article 3 regulates market provision and commissioning. For calibrated scales, Annex 1 of this Directive is important. Here the essential requirements for non-automatic calibrated scales are presented.
What are the procedures?
In addition to calibration, there is also factory calibration, also called ISO calibration. This is carried out by the manufacturer or a qualified person/company. There is no clear definition of what to do here. The manufacturer himself determines the extent of the test. OMEGA Waagen GmbH proceeds with factory calibration as in calibration. We are guided by DIN 45501, which also defines the specifications for the calibration of a scale.
DAkkS calibration is another form of documented testing of a scale. Here, as with calibration, it is clearly defined how the balance is to be checked. The results are output in a test log and serve as proof of the correctness of the weighing results for the user.
Calibration alone is a public act and may only be carried out by the calibration authorities. It is equivalent to the conformity assessment under Directive 2014/31/EU. This is carried out by the manufacturer when a scale is placed on the market for the first time. However, only if the manufacturer maintains a recognised quality management system. A Notified Body shall examine this and grant recognition.
There are a number of implementation variants for the conformity assessment procedure, some of which can be combined. Annex II of Directive 2014/31/EU defines and define the following procedures:
Ø Module B - EU type-examination
Ø Module D - Conformity with the type on the basis of a
Quality assurance of the production process
Ø Module D1 - Quality assurance based on the production process
Ø Module F - Conformity with the design based on a product test
Ø Module F1 - Conformity based on a product test
Ø Module G - Conformity based on an individual test
The old Directive 2009/23/EC was repealed by Directive 2014/31/EU with effect from 20 April 2016.
What is more accurate?
No statement can be made on this subject. The fact is that only a calibrated or conformity-assessed scale may be used in calibrated applications.
For the user, however, a non-calibrated scale can be the better choice. Most of them have a higher resolution. Thisallows the user to obtain better weighing results. It should be noted, however, that a calibrated scale has undergone many tests. Thus, only scales with appropriate approvals can be calibrated.
Approval - A prerequisite for calibration
In order to obtain approval for the components of a scale, an elaborate test procedure is required. The components are checked according to the respective OIML guidelines. It shall be determined to what extent the component may be used in duty-based traffic.
After successful completion of all tests in accordance with the OIML Directive, an accreditation is granted by an accredited testing body. Here is an example of an approval for our evaluationselektronik WA-01:
Without approval, a scale is not calibrated. Approval places very high demands on the components and not without reason. This lays the foundation for reliable weighing results over many years.
Execution of the calibration
How the calibration of a scale is carried out is described in DIN 45501. In addition to checking the documentation of the balance, the approvals are also checked. A compatibility certificate must be created. This shows that the individual components in combination meet the requirements for the desired balance.
The metrological test consists of several steps. The zero position must be checked, as must the overload. A test with normal load, usually full and half normal load is performed. Corner checking ensures that a correct result is displayed even when the load is off-the-board. The hysteresis test includes at least 5 checkpoints. They must include the minimum load and maximum load. The other checkpoints must be close to the values where the error limits change.
Unlike a factory calibration or DAkkS calibration, the actual deviation of the balance is not shown to the customer. The affixing of the calibration marking ensures that the balance operates within the error limits.
The error limits depend on a number of factors. We limit ourselves to the error limits of a Class III scale in this article. In a single-range scale, the weighing area is divided into three areas. In the lower range, the error in the conformity assessment may be 0.5 x e, in the middle range 1 x e and in the upper range 1.5 x e. "e" stands for the calibration value, i.e. the display step. The traffic error limits are twice as high.
The following example illustrates these explanations:
Floor scale with values Max 3,000 kg, Min 20 kg, e = 1 kg
Ø 0 - 500 kg - 0.5 kg
Ø 500 - 2000 kg - 1 kg
Ø 2000 - 3000 kg - 1.5 kg
We do not carry out the calculation further at this point, but we are happy to answer your questions on this subject in a personal interview. Just contact us.
Calibrated counting scales
Are there calibrated counting scales? This question is asked very often and we answer it with a clear NO. The counting function of a scale can never be calibrated. This is clear from all directives, laws and regulations. Or rather, it doesn't come out of it. A counting function is not mentioned in any legal basis. Conversely, this indicates that the counting function is not calibrated.
There can still be a calibrated counting scale, but only the determined weight is to be used in calibration traffic, but not the determined number of pieces. If you have a calibrated counting scale, you may use the weight in calibrated traffic. So, for example, 1 kg of screws cost 5 EUR. But not the number of pieces of, for example, 50 screws.
How a calibrated scale must be labelled is described in Directive 2014/31/EU. From Article 15 onwards, the directive shall provide for labelling. It also incorporates Regulation (EC) 765/2008 Article 30, which sets out the presentation of the CE marking.
The metrology marking is based on the letter "M" and the last two digits of the year in which the marking was affixed, framed by a rectangle. The height of the rectangle corresponds to the height of the CE mark. So far as quoted from the directive.
The following data must be present on the type plate of a calibrated scale:
Ø CE marking
Ø "M" with the annual ID
Ø Identification number of the notified body(s)
Ø NUMBER of the EU type-examination certificate
Ø Name of manufacturer, trade name or trademark
Ø Accuracy class in an oval
Ø Type, batch or serial number
Ø If necessary, division value if it deviates from the calibration value
Ø Special temperature marking
Further data may be required and depend on the equipment of the scale and / or the use. Here we show a type plate for a calibrated scale:
The directive also gives clear instructions for affixing. The data must be clearly visible and legible permanently affixed to the device. They must be placed before they are placed on the market and must not be removed or destroyed when removed. Alternatively, a safety mark can be affixed in such a way that it is destroyed when the label is removed.
Which calibrated scales do we have?
OMEGA Waagen GmbH has the right calibrated solution for every application in industry, retail, logistics and agriculture. For all scales you will also find calibrated variants in our product range. As this topic is not always easy, we are happy to support you in your selection.
Through specific questions, we find the best balance for your application, so that you can pursue your core business with certainty. Even after the purchase, there are still a lot to consider, such as registering the balance with the responsible calibration authority. We support you in this. When the post-calibration is imminent, we are also there for you. We check the scale sit professionally and carry out the calibration preparation. With the calibration office we coordinate an appointment and let the post-calibration take place. If necessary, we will provide you with a replacement scale for the period so that you do not waste any time.
Service at its best - less is not good enough for our customers!