FAQs

You can create and view a quote directly online using our quote generator or contact our testing service sales:
07433/9933-196 or recalibration@kern-sohn.com

Applies to all calibrations in the factory KERN:

Send your measuring instruments to the following address:

KERN & SOHN GmbH
Kalibrierlabor
Ziegelei 1
72336 Balingen
Germany

Please send your order documents and our order form (important: invoice address and delivery address, if different).
If you would like to make demands on our optional express calibration service, please also put our advice for express calibration onto the package.

You are not tied to an appointment - send your weights or your devices just when it is possible in your production process. The inspection and calibration takes about 4 working days (weights of class E1 and reverification variant) in the KERN laboratories. After completed calibration your measuring equipment will be returned together with the calibration certificate.

If repairs or adjustments are necessary, we will contact you. The processing time may increase expense dependent.

For a calibration on site:

Please contact our test services On-Site:

+49 7433 9933-400
testservices-onsite@kern-sohn.com

To access the status of your order, please click here.

Weights have to be recalibrated periodical under the appropriated norm. There is a possibility that the measuring results of the renewed calibration of the weights do not comply with the measuring results of the previous calibration.

There are multiple reasons for this apparently change which mostly collaborate:

• Every calibration is only possible under certain accuracy. The accuracy of the determination will be specified in the form of the expanded uncertainty together with every measuring result. With a probability of 95% it describes in which range of the specified value the actual value of the weight is. In theory it is possible that the difference of the measuring results of two calibrations of the same weight is slightly greater than the specified uncertainty.
• If a weight will get lighter this usually depends on the handling of the weight. Every even careful contact or movement of a weight can dissipate odd lots of the weight's material, also the grip by forceps or the Arrangement on the balance. Often the traces of this removal cannot be recognized with the naked eye. So the constant use can effect significant changing of the mass.
• A weight can also get heavier between two calibrations. Reason for that usually are invisible deposits of particulates of the ambient air in which the weight is stored and used. Another reason could also be inappropriate handling of the weight, for example bare-handed contact or contact with unsuitable liquid. Although a weight will be dry-cleaned before every calibration it is possible that significant diposits in the warpings of the material (the "pores" of the surface) will remain. Also the international prototype of kilogram (primary kilogram), which is handled with high Diligence, is measurable changing. The reason for this could not conclusively be answered yet.

If the renewed calibration of a weight shows a too high modification it is contemplable to shorten the recalibration interval. This is specially recommended in case of the weight does no longer comply with the required tolerances confirmed in the calibration certificate.

The requirements for the weighing room can be found here.

Information on the appropriate calibration weight can typically be found in the operating instructions of your scale under the technical data. You can find high-quality and inexpensive weights in our webshop.

For KERN balances you can easily find the right weight for the balance in our webshop under "Accessories".

If you cannot find information on a suitable weight for your scales, we recommend the following procedure:

• The nominal value of the weight should be between 80% and 100% of the capacity of the scale (Max).
• The accuracy (permissible tolerance) should be less than or equal to the readability of the scale.
  You can find the OIML tolerances here.

Calibration:
Determination of accuracy worldwide by a laboratory which is accredited to DIN EN ISO/IEC 17025. Traceability to internationally recognised standards. The DAkkS calibration certificate confirms both the metrological characteristics of the checking equipment and the general requirements for the monitoring of checking equipment.

Verification:
Testing to verification error limits to protect the consumer. When introducing balances and weights onto the market, they are subject to EU directives. The subsequent monitoring of the market is regulated at a national level, in Germany through the MessEG (Weights and Measures Act) and MessEV (Verification ordinance).

You will find further differences between calibration and calibration here.

Information on verification periods can be found here.

Calibration:
Determination of accuracy worldwide by a laboratory which is accredited to DIN EN ISO/IEC 17025. Traceability to internationally recognised standards. The DAkkS calibration certificate confirms both the metrological characteristics of the checking equipment and the general requirements for the monitoring of checking equipment.

Verification:
Testing to verification error limits to protect the consumer. When introducing balances and weights onto the market, they are subject to EU directives. The subsequent monitoring of the market is regulated at a national level, in Germany through the MessEG (Weights and Measures Act) and MessEV (Verification ordinance).

You will find further differences between calibration and calibration here.

In general as the manufacturer or calibration laboratory we cannot give you a clear specification for the recalibration interval of a measuring instrument. The change of a measuring instrument depends on the instrument itself, the way of use, the environment and of course on your precision requirements. Usually we recommend to start with a recalibration interval of 12 months (or less in case of extremely stressed usage). With the second calibration you are already able to make a statement about the stability of the measuring instrument and if an increase of the recalibration interval to 24 months is possible. Of course a accidental defect or damage is always possible. So the maximum assigned recalibration interval after years is thought to be more a question of the entrepreneurial risk.

An accreditation is a process procedure according to which an authorized body (for example, the accreditation body of the DAkkS) granted a formal recognition by a certain competence. Click here to see the accreditations of KERN.

Calibrations carried out by accredited laboratories guarantee reliable measurement results for the user and increase customer confidence and competitiveness in the national and international market. They are a metrological basis for bonitoring the measuring and testing equipment within the framework of quality management. With KERN you have a competent partner at your side who fulfills all these requirements reliably.

The KERN calibration laboratory currently has an indefinite accreditation. For this reason, no expiry date is specified in the accreditation certificate.

Open-ended accreditations:

In the state-regulated sector, accreditations are normally issued without a fixed expiry date. These remain effective until the German Accreditation Body (DAkkS) withdraws, suspends, restricts or amends them, or until the accredited organisation itself withdraws the accreditation.

Accreditation can be restricted if important requirements for accreditation cease to apply or if the accredited organisation does not cooperate with the required surveillance. Market feedback or the results of market surveillance can also lead to a limitation.

Temporary accreditations:

In certain cases, particularly in the government sector, if the law prescribes a time limit, accreditations are only granted for a certain period of time. This also applies to all accreditations outside Germany, the EU and the EEA in the non-governmental sector.

These time-limited accreditations end on the date specified in the notification and the associated certificate. It is necessary to initiate a procedure for reaccreditation in good time.

Every body experiences a relatively small loss of weight in air (buoyancy). This must be taken into account for accurate weighing procedures. In order to avoid this "distortion" in daily use, all weights are adjusted to the unit specifications as given in R111 OIML recommendation. (air pressure 1.2 kg / m³ and material density 8000 kg / m³)

During the calibration of weights the tolerances of OIML R111:2004 are used. For this it is necessary to consider the uncertainty.
Regarding the OIML R111:2004 this should be 1/3 of the max. perm. error, so the max. perm. error minus uncertainty is 2/3 of the OIML tolerance.

The uncertainty includes for example:

• deviation of the normal
• buoyancy
• variations in temperature
• tolerances of the Balance

A weight is out of tolerance if it is not within the max. perm. error minus uncertainty.

Calibration "as found/as received" is the determination of the current state of the balance before possible interventions such as an adjustment or repair.
I.e. a calibration is carried out in the current state of the balance, even if the values should not be within the tolerance. These values are recorded during an "as left/as returned" calibration and shown in the calibration certificate.

The calibration "as left/as returned" represents the calibration and listing of the measured values after possible interventions such as an adjustment or a repair.
I.e. the calibration certificate shows the measured values after this intervention.

Valid only for the sending in of balances:
As a rule, the calibration is performed "as left/as returned" and only this is shown in the calibration certificate. If you also require the calibration "as found/as received", please note this in your order documents. You will then receive a calibration certificate with the recording of both measured values in the form of two states.
Please note that the calibration "as found/as received" is an optional service which will be charged separately.

Die Unterscheidung zwischen Genauigkeit und Empfindlichkeit wird in der Ph.Eur. 2.1.7. sehr ausführlich beschrieben.
Kurz zusammengefasst:
Die „Genauigkeit“ einer Waagenanzeige („stimmt der angezeigte Wert“) wird durch mehrere Parameter der Waage beeinflusst:
* Wiederholbarkeit: Werte schwanken zufällig
* Linearität: Doppelte Last ist nicht zwingend doppelte Anzeige
* Außermittige Belastung: Position des Gewichts beeinflusst Anzeige
* Empfindlichkeit: quasi die Justierung der Waage / Steigung der Kennlinie

During the calibration it is possible that a weight has to be replaced / exchanged. This can have the following reasons:

• The weight is out of the permissible tolerance and cannot be adjusted.
• The weight is out of the permissible tolerance and replacement is more favorable than adjustment of the weight.
• The weight shows such heavy signs of use that further use in safe compliance with the tolerances is no longer possible (e.g. due to rust, oxidation, etc.).

Should it be necessary to replace a weight, you will be informed of this in principle, unless you have agreed to a replacement in advance without consultation.

You can also find more information about our standard procedure here.

Within the scope of calibration, it is possible that the adjustment of a weight is necessary because it no longer complies with the permissible tolerances. The adjustment of a weight depends on its design:

• Weights with adjustment chamber
  

  If an adjustment chamber is available, the weight value of the weight is adjusted by adding or removing adjustment material.

  The design of the calibration chamber depends, among other things, on the accuracy class of the weight. The calibration chamber is located inside the weight and is usually sealed with a lead seal or screw cap.

  This adjustment chamber is carefully opened by our calibration laboratory and the adjustment material (e.g. lead beads) is either removed or added. The adjustment chamber is then closed again in a professional manner.

  It is recommended that the calibration chamber only should be opened when necessary and only by the calibration laboratory.

• Weights without adjustment chamber
  

  Weights of accuracy classes E1 and E2 as well as wire and plate weights do not have an adjustment chamber.
  The adjustment is made by mechanical removal (e.g. polishing) here.

If it is necessary to adjust a weight, you will always be informed of this unless you have agreed to the adjustment in advance without prior consultation.

You can also find more information about our standard procedure here.

If you have sent us a weight set for calibration in which a weight is missing, we will kindly offer to complete the set for you.

For this purpose, you will receive an inquiry with the specification of the missing weight as well as the price. If you agree to the addition, it will be noted in the calibration certificate that the weight has been added.

You can also find more information about our standard procedure here.

Unfortunately, it sometimes happens that weights become magnetic due to various factors. Since this can affect the conventional weight value and your weighings, we recommend - where technically possible - demagnetization in these cases.

With our equipment we can usually demagnetize your weights professionally. If demagnetization is not possible or not successful, the weight must be replaced.

You can also find more information about our standard procedure here.

Information on the appropriate calibration weight can typically be found in the operating instructions of your scale under the technical data. You can find high-quality and inexpensive weights in our webshop.

For KERN balances you can easily find the right weight for the balance in our webshop under "Accessories".

If you cannot find information on a suitable weight for your scales, we recommend the following procedure:

• The nominal value of the weight should be between 80% and 100% of the capacity of the scale (Max).
• The accuracy (permissible tolerance) should be less than or equal to the readability of the scale.
  You can find the OIML tolerances here.