Here you can find answers to frequently asked questions (FAQs):
How to get price informations?
How do I place an order?
Applies to all calibrations in the factory KERN:
Send your measuring instruments to the following address:
KERN & SOHN GmbH
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 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.
How can I check the status of my order?
Please click here.
What´s the difference between calibration and verification?
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.
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.
How long is the validity of a DAkkS calibration?
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.
What is accreditation?
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.
What does conventional mass mean?
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)
In which context are the max. perm. error and uncertainty?
During the calibration of weights the tolerances of OIML R111-1 are used. For this it is necessary to consider the uncertainty.
Regarding the OIML R111-1 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
- variations in temperature
- tolerances of the Balance
A weight is out of tolerance if it is not within the max. perm. error minus uncertainty.
How does a weight change mass?
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.