Service - Calibration

What is the difference between a DKD/DAkkS calibration and a factory calibration?

With a DKD/DAkkS calibration, the customer receives a DKD/DAkkS certificate, with the factory calibration, a 3.1 certificate in accordance with DIN EN 10204. For more information about this topic, see our "Calibration" flyer.

What does calibration mean?

To calibrate in measurement technology means to determine the deviations in the complete measuring instrument. With calibration there is no technical intervention at the measuring instrument, such as zero point adjustment, span and linearity setting, etc.. With indicating measuring instruments calibration establishes the measuring deviation between the display and what is claimed to be the correct value of the measurand. For material measurements, for example dimensions, the measuring deviation is determined by measuring the difference between the marking and the correct value. For measuring chains one determines the deviation between the measured value of the output signal and the value that this signal should have with an ideal transfer characteristic and a given input value.

What is adjustment?

Adjustment means setting or alignment of a measuring instrument (also a material measure) so that the measuring deviations are made as small as possible or that the magnitudes of the measuring deviations do not exceed the error limits. The adjustment, therefore, requires an intervention which, in most cases, permanently alters the measuring instrument or the material measure, e.g. repositioning the pointer or fitting a new dial.

What is verification?

The verification of a measuring instrument (also a material measure) includes the testing, from the competent calibration authority in accordance with the calibration instructions to be carried out, and the stamping. Through the testing it is determined whether the measuring instrument submitted meets the calibration specifications (meaning whether it, in the nature of its properties and its metrological properties, satisfactorily meets the requirements), in particular, whether the magnitude of the measuring deviations does not exceed the error limits (n). Through the stamping, it is certified that the measuring instrument has satisfied these requirements at the time of the testing, and through its nature is expected, if handled in line with the codes of practice within the calibration interval, to remain within the specified tolerance range. Which instruments are subject to obligatory verification and which are excluded from this is regulated by law.

What is the maximum pressure that the WIKA DAkkS laboratory is certified up to?

10,000 bar

What is the minimum number of calibration points in a calibration report (DKD/DAkkS certificate) for pressure?

for pressure measuring instruments with an accuracy class of <= 0.6 % min. 9 points
for pressure measuring instruments with an accuracy class of > 0.6 % min. 5 points

How frequently, or after what interval, is the recalibration of a pressure measuring instrument required?

for pressure measuring instruments with an accuracy class of <= 0.6 %  annually
for pressure measuring instruments with an accuracy class of > 0.6 % every 2 years
for pressure balances, every 5 years.

For which pressure and temperature ranges have the calibration laboratories been accredited?

Positive or negative gauge pressure:  -1 … +8,000 bar
Absolute pressure:  0 … 8,001 bar
Differential pressure: 0 ... 10 bar at a stat. pressure of 250 bar

Temperature:  -196 ... +1,200 °C

What is the German physical and technical test institute (PTB)?

The PTB, Braunschweig and Berlin, is the metrological state institute and Germany's highest technical body for metrology. It stores and develops the national standards for implementing the SI units and ensures their comparability on an international level by cooperation with other state institutes.

What is the German Calibration Service (DKD)?

In accordance with the Units and Time Act (EinheitZeitG), the PTB is responsible for ensuring the uniformity of measurement. This includes, in particular, the propagation of the units of measure within the meaning of measurement technology traceability. For the propagation of the units, the PTB primarily operates accredited laboratories. To promote uniformity in metrology, and with the aim of an extended professional support, on the 3rd May, 2011, a committee was established with the PTB for the development of measurement technology bases for calibration, in which the PTB and accredited calibration laboratories cooperate closely.

This body has the title “Deutscher Kalibrierdienst (DKD)” - German Calibration Service - and is under the direction of the PTB.

How do you recognise an accredited body?

All bodies accredited by the DAkkS can prove their status by an accreditation certificate. In sovereign territory, the certificate is provided with the federal eagle. Moreover, the bodies can signal their accredited status by using the DAkkS accreditation symbols on test reports and certificates and thus document the high quality of their evaluation service. The symbol consists of the protected DAkkS logo and a unique registration numbere. On its website, the DAkkS makes available a database of all accredited bodies (www.dakks.de).

What advantages are offered by accreditations?

For the company, accreditations promote international comparability and recognition of certificates and test reports. This transparency makes it easier for companies to gain access to national and international markets. Moreover, proof of accreditation is often the prerequisite of certain norms of "potential customers". The business relationship is only made possible by virtue of accreditation. The consumer can rely on the data on the calibration certificate. Moreover, he knows that, depending on the data given, standards, regulations and international recommendations are thereby guaranteed (conformity statement). Finally, he can rest assured that the DKD/ DAkkS certificate is recognised internationally within wide boundaries.

Why should equipment be calibrated?

To ensure consistent quality of the manufactured products, quality management according to the family of standards DIN EN ISO 9000 has been in force for years and is indispensable for many companies. This standard requires that all quality-relevant features of a product must be tested and, when doing so, retraceable inspection equipment is regularly used. Calibration ensures that the measured results are internationally comparable and product liability risks are minimised - an important prerequisite for competitiveness on tomorrow's markets.

What is an accreditation?

Confidence in calibration stands or falls on the competence of those who deliver the assessment service. Many of these conformity assessment bodies substantiate the quality of their own work through an accreditation. In this process, they demonstrate to an independent accreditation body that they complete their activities competently, in compliance with legal and normative requirements and to an internationally comparable level. In Germany, only DAkkS acts as a national accreditation body.

What is a standard?

Standard (VIM): "Material measure, measuring instrument, reference material or measuring device intended to define, materialise, conserve or reproduce a unit or one or several values of a quantity."

What is a national standard?

A standard approved by national decision as basis for the determination of values of all other standards of the quantity in question (SI unit).

What is a reference standard?

A standard, in general of the highest available accuracy at a given place or at an organisation which can be used to carry out measurements there.

What is a working standard?

A standard routinely used for calibrating or testing material measures, measuring instruments or reference materials.
- a working standard is usually calibrated by means of a reference standard
- a working standard usually used for guaranteeing that measurements are carried out correctly is called a test standard.

How is a calibration interval determined?

To ensure that correct measurements can be carried out permanently, the inspection equipment used must be monitored or calibrated at regular intervals. This period of time corresponds to the calibration interval. The user of a calibration item has sole responsibility for defining the exact calibration interval. There are, however, many different factors that effect the determination of the calibration interval. They include, for example, the required measurement uncertainties, defintion of standards and directives, operating conditions of the inspection equipment, frequency of use, subsequent costs caused by measurements using a defective instrument and the manufacturer's recommendation.

For which electrical measurement parameters have the calibration laboratories been accredited?

DC current:  0 mA … 100 mA
DC voltage: 0 V … 100 V
DC resistance: 0 Ω … 10 kΩ

For which pressure ranges has the mobile calibration service been accredited?

On-site calibration:
Gauge pressure:  -1 bar … 8,000 bar
Absolute pressure:  0 bar … 8,001 bar

Calibration vans:
Gauge pressure:  -1 bar … 4,000 bar
Absolute pressure:  0 bar … 60 bar

Can a 3.1 acceptance test certificate/factory calibration certificate be used for traceability?

No. A 3.1 inspection  certificate/factory calibration certificate is only used to list single measured values and can't be used for traceability. The statement that a 3.1 inspection certificate/factory calibration certificate documents the traceability is only acceptable if:

  • the reference standards used are traceable and
  • an accredited calibration procedure (validated procedure)  described in a normative document, was properly used.

On cost grounds, this is only used in a reduced form in many cases. 3.1 inspection certificates/factory calibration certificates from accredited testing and calibration laboratories must be treated like calibration certificates from non-accredited institutes.

What is the difference between a calibration and a verification?

The difference between a calibration and a verification is that the verification must be made by a public authority. It can also be a legal requirement in some cases. Calibration is the regular checking of measuring instruments. For this purpose, a reference measuring instrument is used which is traceable, so that it conforms with the national standard. Both procedures describe only the checking of the display quality, not its correction.

What is the difference between a calibration and an adjustment?

If an instrument is calibrated and the deviation is too large and is no longer within the manufacturer's specifications, the instrument will be reset. This process is known as adjustment.

What are the consequences if instruments are not regularly calibrated?

Every measuring instrument is subject to ageing as a result of mechanical, chemical or thermal stress. As a result, over time, it provides changing measured values. If the instrument has become inaccurate, this can lead to disruptions in the process or even trigger safety risks. Through calibration, this can be detected in good time.

What is the difference between the factory calibration and the calibration in accordance with ISO 17025?

The difference is that the factory calibration only documents the deviation from the reference, while ISO 17025 calibration ensures traceability to the national standard. In addition, along with the deviation, the hysteresis and the repeatability are also documented. This is also internationally recognised.

How does a calibration certificate in accordance with ISO 17025 differ from a factory calibration?

With a calibration in accordance with ISO 17025, many more key figures are determined and the expanded measurement uncertainty is developed graphically. This is, therefore, also recognised worldwide by all operators.