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Frequently asked questions about calibration

Calibration is a complicated issue. That’s why we have prepared some straightforward answers to the questions we often receive from our customers.

Calibration is a key issue – to ensure product and service quality, and to meet legal requirements. But calibration is also a complicated issue. That’s why we have prepared some straightforward answers to the questions we often receive from our customers.

Q: Why do I need to calibrate my instruments?
A: Regular calibration provides you with:

  • Knowledge and evidence of how your instrument measures – now and over time
  • Reliability – the confidence that you know your instrument works correctly

According to the International Laboratory Accreditation Cooperation (ILAC), the purpose of calibration is:

  • To know the uncertainty that can be achieved with the measuring instrument
  • To confirm whether or not there has been any alteration of the measuring instrument that could create doubt about the results
  • To improve the estimation of the deviation between a reference value and the value obtained using a measurement instrument, as well as the uncertainty in this deviation, at the time the instrument is actually used

Q: How can I see when my equipment is calibrated?
A: Calibration Certificate is always provided with equipment calibrated at Brüel & Kjær service centers. The certificates are also accessible from the Online calibration data webpage from Brüel & Kjær’s Cloud solution. Each calibrated item is accompanied with a sticker printed with pertinent data such as serial number and calibration date.

The sticker is attached to the equipment when possible. For small items like transducers with insufficient space for stickers, the sticker is attached to the box in which the item is delivered. If no free space available on the equipment and there is no dedicated box, the sticker is delivered together with the printed certificate.

Q: Are diaphragms cleaned as part of microphone calibration?
A: Dirty diaphragms are not cleaned as part of the calibration. Cleaning the diaphragms affects the performance of the microphone and violates the calibration history.

Diaphragm cleaning can be arranged upon special agreement with Brüel & Kjær. In such cases, two calibration certificates are issued:

  1. Calibration as received
  2. Calibration after repair/adjustment.

Q: Why should I calibrate a new instrument that came directly from the factory?

A: Sometimes it will be a legal requirement and sometimes you will need to chart changes in the instrument over time. In these cases, you will need to track calibration data from the time of the initial purchase.

Q: When should I re-calibrate my instrument?

A: We recommend that you begin a calibration history from day one and re-calibrate once a year. This enables you to compare your measurement results over time.

Q: Is it sufficient to send in my instruments for calibration every second year?

A: It depends on how accurate you want it to be. Do you want to risk months or years of untrustworthy measurement results? This makes it difficult to pinpoint exactly when the faulty measurements first occurred. This is why we strongly recommend annual calibration for all devices.

How often you calibrate your instrument is a balance between risk and cost. The shorter the period between calibrations, the lower the risk of questionable measurements. We consequently recommend annual calibration for instruments.

Equipment used on a daily basis will have a shorter calibration cycle than equipment used, for example, once a month.

Q: Our instruments are used in our internal R&D department only, and there are no public or quality standards we have to follow. Why should we calibrate?

A: If you need to compare measurement results across a period of time, we recommend that you calibrate your instruments. This will provide you with a certificate containing measured values if one of your products or research findings is later accused of being faulty.

Q: What is the difference between accredited and traceable calibration?

A: Accredited national and international bodies, such as the ILAC, approve accredited calibration. Traceable calibration is conducted according to these same standards, and ensures that calibration results are correct, but an official governing body does not explicitly approve the results.

Q: Why should I choose accredited calibration? Isn’t traceable calibration enough?

A: If you or your customers want to publicize the measurement results or fulfil requirements in quality processes, such as ISO certification, you must have accredited calibration. And the certificate can be used as legally acceptable documentation.

Q: Is it sufficient to use a calibrator?

A: No. A calibrator is used to verify the instrument just before and after a field measurement. This is not a replacement for periodic calibration in a laboratory.

Q: What is required for a calibration laboratory in order to achieve accreditation?

A: You will need a quality policy that fulfils the requirements of ISO 17025, including physical premises, methodology, procedures, traceability, technical skills, and record documents.

Q: What does an accredited certificate from Brüel & Kjær contain?

A: You get a certificate with measurement values and an uncertainty budget according to ISO 17025.

Q: Can I use a DANAK certificate in other countries?

A: Yes. Through mutual recognition with other accreditation bodies, DANAK is accepted on the same level as individual national accreditation standards. DANAK is a member of the European Cooperation for Accreditation (EA) and International Laboratory Accreditation Cooperation (ILAC).

Q: Can I compare an older certificate from another laboratory with a new one from Brüel & Kjær?

A: Yes

Q: How can I get a copy of a previous calibration certificate?

A: You can go to and download calibration information, provided you have the instrument type number and serial number. You need to have a profile on and be logged in. Alternatively, please contact your local service centre.

Q: How can I find the price for a specific calibration?

A: Please contact your local Brüel & Kjær representative.

Q: How do I order calibration?

A: Just fill in our service request form.

Q: How do I know that you have received the instrument I sent, and how can I follow its progress?

A: According to standard process customers receive the following notifications when Brüel & Kjær has received equipment for service:

  • An acknowledgement email when equipment is received.
  • An Order Confirmation when equipment and Purchase Order are received.
  • A Delivery note with tracking information when calibration is performed and equipment is returned.

Please note that there are minor deviations in the process from country to country so not all notifications are issued for all countries.