AA Calibration
Accredited calibrations are carried out for measuring instruments, reference materials, and dimensional standards for specific measurands and measurement ranges, which are defined individually for each laboratory in its accreditation.
The issued AA calibration certificates serve as evidence of metrological traceability to national or international standards, as required, for example, by the DIN EN ISO 9000 family of standards and DIN EN ISO/IEC 17025.
AA calibrations do not have a legally defined validity period. The operator is responsible for ensuring that recalibration is performed within an appropriate time frame. Recalibration intervals of approximately one year are common.
Accreditation
Formal recognition of a high level of performance that has been demonstrated in accordance with recognized international standards and is regularly reviewed by an authorized body.
The authorization to issue accredited calibration certificates, for example for balances, requires that the calibration laboratory is accredited according to DIN/ISO 17025 “General requirements for the competence of testing and calibration laboratories.”
adjusting
-> Adjustment
Adjustment
Precise setting of a measured value through professional intervention in the measuring system.
In the case of balances: either using an external test weight via the adjustment function (CAL or CAL button), or with the internal adjustment mechanism or adjustment circuit.
Necessary in cases of temperature changes, altered environmental conditions, relocation, etc.
Daily routine checks are recommended.
The term "calibration" was formerly also used for adjustment but today refers to a different process.
Akkreditierung Austria Kalibrierung
Application accuracy
Allowance for measuring uncertainty during practical use of a balance. Is given in the appendix to the AA calibration certificate.
as found
This term applies to the calibration of the test equipment on site.
Calibration "as found" 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 found" calibration and shown in the calibration certificate.
as left
This term applies to the calibration of the test equipment on site.
The calibration "as left" represents the calibration and listing of the measured values after any interventions such as an adjustment or a repair.
I.e. the calibration certificate shows the measured values after this intervention.
as received
This term applies to the sending of the test equipment to the permanent laboratory.
Calibration "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 performed in the current state of the balance, even if the values should not be within the tolerance. These values are recorded "as received" during a calibration and shown in the calibration certificate.
as returned
This term applies to the sending of the test equipment to the permanent laboratory.
The calibration "as returned" represents the calibration and listing of the measured values after any interventions such as an adjustment or a repair.
I.e. the calibration certificate shows the measured values after this intervention.
Calibration
Calibration is the process of checking and determining the accuracy of a measured variable without interfering with the measuring system. The calibration certificate contains the measured value with an indication of the respective measurement uncertainty. It is possible to determine whether a tolerance limit is being adhered to or not. Industry requires the calibration of measuring instruments so that, for example, parts produced at different locations can be easily connected to each other. Calibrations must be repeated at appropriate intervals, for which the user is responsible. We recommend having the measuring instruments recalibrated every 6 months for intensive (daily) use and every 12 months for normal (weekly) use.
calibration weight
-> External test weight/adjustment weight (formerly calibration weight)
Certification
Commercial error limit
Permitted tolerance (plus and minus) of measuring devices where verification is mandatory when used within their verification validity period. This tolerance is double the permissible error limit, in so far as this is not specified otherwise in the weights and measurers act.
Conformity assessment
Conformity assessment, verification
Procedure for confirming warranted characteristics in accordance with recognised rules. For balances this relates to conformity assessment/verification.
Conformity declaration from the manufacturer
The manufacturer declares that the product fulfils the applicable EU directives. With electronic balances this is always in conjunction with the CE mark.
Control of measuring equipment in the QM System in conjunction with quality standards
An organization certified according to a quality standard such as DIN EN ISO 9001 ff., for example a manufacturing company, commits as part of its quality management system to comply with defined quality standards. Precisely operating measuring instruments are an essential prerequisite for this.
DIN EN ISO 9001:2015-11 states in section 7.1.5 "Resources for Monitoring and Measurement" that measuring equipment must be calibrated at specified intervals and prior to use. The measuring instruments and standards required for this must:
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be traceable to international or national standards
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have a known measurement uncertainty
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be clearly and uniquely identified
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have their verification documented
The calibration certificate with accreditation symbol meets all these requirements.
Conventional mass
Every object experiences a relatively small loss of weight in air (buoyancy). This must be taken into account for precise weighing.
To eliminate such “distortions” in daily use, all weights are adjusted to the standard conditions defined in OIML Recommendation R111 (air density: 1.2 kg/m³ and material density: 8000 kg/m³).
deactivation
DIN EN ISO 9000ff
end calibration
external calibration weight
-> External test weight/adjustment weight (formerly calibration weight)
External test weight
-> External test weight/adjustment weight (formerly calibration weight)
External test weight/adjustment weight (formerly calibration weight)
Used for adjusting or checking the accuracy of the balance. The external test weight can be accreditedly calibrated at any time, even retrospectively.
Factory calibration certificates
The testing of measuring instruments for accuracy is carried out according to a recognized but non-accredited procedure – this is the key difference compared to accredited calibration.
Final calibration
A final calibration refers to the last calibration that must be performed before the deactivation of a measuring instrument.
The purpose of this calibration is to determine whether the instrument met the required tolerances during its period of use since the last recalibration.
If the tolerances were not met during the usage period, the impact on previously performed calibrations must be assessed and, if necessary, corrective actions must be initiated.
Gravitation
Gravitational acceleration
Very important influence for precise electronic balances. Due to the varying influence balances have to be adjusted at the location of use.
Gravitational force
Internal test weight
Like external test weight, but installed in the balance and powered.
International validity of AA calibration certificates
Akkreditierung Austria is a member of both the EA (European cooperation for Accreditation) and ILAC (International Laboratory Accreditation Cooperation). This ensures the recognition and validity of AA calibrations and AA calibration certificates almost worldwide.
ISO 9000ff
ISO 9000ff, DIN EN ISO 9000ff
Quality Management System in the form of a DIN Norm for quality assurance in a factory.
ISO calibration
Linearity
Linearity/Precision
Greatest deviation of the weight displayed of a balance with regard to the value of the respective test weight in terms of plus and minus across the whole weighing range.
Measurement uncertainty
It is determined for each balance according to a precisely given test method and documented in the Calibration certificate. It depends on various factors, both internal and external. The measuring uncertainty of a measuring device is an objective measure of its accuracy and is therefore an accurate statement for its appropriate use.
Measuring uncertainty
Minimum load [Min]
Lower limit of the verifiable weighing range. Is markes on the verification mark. The function of the balance is also given below the minimum load.
Minimum sample weight
Indicates the smallest weight which can be determined, depending on the process accuracy required.
Notified body
Neutral and independent, predominantly government bodies, which are formally apppointed by the EC. They are engaged in the field of verification for conformity evaluations (initial verification) and type-approval test within the scope of type approvals.
OIML
In the "International Organization of Legal Metrology (OIML)", representatives from nearly 100 countries work on harmonized construction and testing regulations for all measuring instruments.
Within the OIML certification system, certificates issued by member states confirm that a specific type of measuring instrument complies with OIML recommendations.
This allows a device type that has been tested and approved in one country to be accepted in another without the need for repeated testing.
OIML Directive R111 defines design-related characteristics for test weights, such as material, surface finish, markings, structure, shape, etc.
Precision
Readout [d]
Smallest readable weight increment on a digital display.
Reproducibility (standard deviation)
Sequenced measure of conformity in repeated weighing (e.g. balances) subject to the same conditions. Mostly 1 [d] or less. Quality feature.
Resolution of a balance
The resolution is calculated from the weighing range [Max] divided by the readout [d], e.g. [Max] 420 g:[d] 0.001 g = 420.000 points. The resolution is a quality feature - the higher, the better.
Traceability
A prerequisite for any reliable measurement is the complete and uninterrupted proof that a measuring instrument is traceable to the international or national standard.
The most important standards require that all test equipment (e.g. test weights) comply with national or international standards within defined tolerances.
In weighing technology, test weights serve as these standards. They are traceable to the national standard maintained by the BEV (Federal Office of Metrology and Surveying) in Vienna, which in turn ensures traceability to the International System of Units (SI).
This prevents measurement errors caused by inaccurate test equipment.
Uncertainty
verification
Verification
A verification, called "evaluation of conformity according to NAWI: 2014/31/EU" for new conceptuality, means the official examination of the accuracy of dimensions, weights, balances and measuring tools according to the law of dimensions and weight. The verification is required by the state and protects consumers. Only balances with approved design and only weights according to OIML of classes E2, F1, F2 and M1 can get a conformity assessment.
verification class
Verification classes of balances
Verification classes of balances, verification class
Class I - analytical balance (precision balance)
Class II - precision balance
Class III - industrial scale (commercial scale)
Verification value [e]
Measure of the verification tolerance, depending on balance, mostly between 1 [d] and 10 [d].
verify
-> Verification
Weighing range [Max]
Is the working range of the balance. The balance can be loaded up to the specified upper limit.