Are All Calibrations The Same?

Routine scale calibration is critical for maintenance and dependability. To ensure every scale is properly calibrated, weights are classified by various styles, certifications, finishes and weights. However, all calibration weights serve the same function: they are known standards used to check and adjust a weighing system.

Why Certified Calibration Weights Matter

Using a calibration weight on a scale or balance is only worthwhile if the calibration weight is within a tolerable weight range. The only reliable way to ensure a calibration weight is within tolerance is to have the weight recalibrated by an accredited metrology laboratory.

Accredited facilities are either state-owned or independent metrology laboratories, such as a calibration weights manufacturer with an onsite metrology lab. Accredited laboratories provide calibration reports that include statements of accuracy or certificates of accredited calibration.

Different Types and Certificates of Weight Calibration

Not all calibrations are the same. The accreditation of the laboratory impacts the calibration, as well as the type and traceability of the calibration. It’s important that weights are calibrated on the correct balance to obtain certification. Lower class weights shouldn’t be calibrated on the highest class of balances, or vice versa.

Weight calibration also requires documentation for:

Tracking weight calibration is essential to maintaining the traceability chain. Maintaining traceability to the international standard (SI) through the National Institute of Standards and Technology (NIST) guarantees that weights calibrated in the accredited laboratory are as accurate as weights calibrated in another laboratory. Depending on how precise the requirements for weighing are, facilities will need different levels of traceability.   

Accredited Calibration

An accredited calibration needs traceability to NIST that includes a nominal mass value plus or minus corrections and uncertainty values.

Non-accredited Calibration

A non-accredited calibration still needs traceability to NIST, which includes actual values and uncertainties.

Statement of Accuracy

A non-accredited, basic statement of accuracy used in non-Legal for Trade applications would state the nominal values represented by the calibration weight and that the weight has been designed and manufactured within specification

Metrology Lab Accreditation

The National Voluntary Laboratory Accreditation Program (NVLAP) is a renowned accreditation program created by NIST. NVLAP reduces unreliable weight calibration by offering third-party assessment and accreditation to testing and calibration laboratories.

NVLAP assesses laboratories with proficiency testing, along with document review. Assessment against the management and technical requirements published in the International Standard, ISO/IEC 17025:2017, is also a component of NVLAP accreditation assessment. NVLAP accreditation reflects laboratory competence, ensuring operations meet NVLAP standards.

Similarly, many laboratories rely on the American Association for Laboratory Accreditation (A2LA) for assessing operations and competency within specific fields, such as calibration.

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