Metrology News

Inside SOP 30: building your first measurement assurance program This month's control-chart series described the instruments; SOP 30 is the score. A process measurement assurance program (PMAP) is the mana... Aug 28, 2026 VIM concept: verification and validation, one letter and one question apart Verification and validation get used interchangeably in quality systems, and the VIM's pair of definitions is the cleanest cure. Verificatio... Aug 27, 2026 Force explainer: from deadweight machines to strain-gauge cells Force traceability starts with the only force we can create from first principles: gravity on a known mass. A deadweight force machine stack... Aug 26, 2026 Inside SOP 1: what belongs on a calibration certificate A calibration certificate is a legal and technical document pretending to be a form. SOP 1 — the very first procedure in the NIST series, in... Aug 25, 2026 Standards profile: ISO/IEC 17043 — who tests the testers Proficiency testing only means something if the scheme itself is competent — the assigned value honest, the items stable and homogeneous, th... Aug 24, 2026 Control charts III: SOP 20 and the standard deviation chart The mean chart of SOPs 9 and 17 watches whether a process's CENTER moves. SOP 20 completes the series with the chart that watches its SPREAD... Aug 23, 2026 VIM concept: influence quantities — measuring one thing while another moves The VIM's influence quantity (2.52) is the concept behind most mysterious measurement disagreements: a quantity that isn't the thing you're... Aug 22, 2026 Inside GMP 12: choosing the right procedure is a metrological decision With a library of sixty procedures, the quiet question is: which one? NIST's GMP 12 exists for exactly that — selecting and applying the app... Aug 21, 2026 Time explainer: what a stopwatch calibration actually verifies A stopwatch calibration sounds trivial — time is, after all, the best-realized unit in the SI. The subtlety is that a stopwatch measurement... Aug 20, 2026 Standards profile: EA-4/02, the uncertainty guide that shows its work The GUM defines the framework; EA-4/02 shows the homework. The European co-operation for Accreditation's mandatory uncertainty guide applies... Aug 19, 2026 Inside SOP 14: gravimetric volume calibration — mass in, litres out The most accurate way to measure a volume is to weigh it. SOP 14 in the library is the gravimetric method for volume standards: fill with di... Aug 18, 2026 VIM concept: repeatability, reproducibility, and the conditions between Precision is not one number. The VIM defines a ladder of measurement conditions, and the standard deviation you quote depends entirely on wh... Aug 17, 2026 Humidity explainer: relative humidity, dew point, and what your hygrometer hides Humidity is the environmental quantity laboratories measure most and understand least. Relative humidity is a ratio — water vapor present ve... Aug 16, 2026 Inside GLP 9: rounding is a metrological act Rounding feels like arithmetic hygiene, but done carelessly it quietly moves results and pass/fail decisions. NIST's GLP 9 — two dense pages... Aug 15, 2026 Standards profile: ISO 376 and the force-proving chain Every tensile test certificate ultimately leans on a force-proving instrument, and ISO 376 is the standard that disciplines them. It specifi... Aug 14, 2026 Control charts II: SOP 17 and check standards as early-warning radar The second procedure in the library's control-chart series, SOP 17, generalizes the idea beyond mass: any measurement process — volume trans... Aug 13, 2026 Pressure explainer: head correction, the metre that moves your pascal Two pressure instruments connected by a metre of tubing can disagree by more than their combined specifications — not because either is wron... Aug 12, 2026 Inside SOP 8: modified substitution — when good enough is exactly right Not every weighing deserves the full double-substitution ceremony. NIST's SOP 8 documents modified substitution: the standard and unknown ar... Aug 11, 2026 VIM concept: MPE is not uncertainty Two numbers get conflated on certificates and datasheets constantly: maximum permissible error and measurement uncertainty. The VIM keeps th... Aug 10, 2026 Standards profile: OIML R 111 and what class E2 really promises When a weight is sold as 'class E2', OIML R 111 is the document making the promise — and the promise is more than a tolerance. The recommend... Aug 9, 2026 Inside GMP 11: setting calibration intervals you can defend 'Calibrate annually' is a habit, not an analysis. NIST's GMP 11 — in the library — is the short, blunt antidote: intervals should come from... Aug 8, 2026 Torque explainer: why ISO 6789 splits design from calibration The 2017 revision of ISO 6789 did something quietly important for torque tools: it split the standard in two. Part 1 covers design conforman... Aug 7, 2026 Control charts I: SOP 9 and the discipline of watching your process A calibration certificate is a snapshot; a control chart is a film. NIST's SOP 9 — first of three control-chart procedures in the library —... Aug 6, 2026 Inside SOP 2: air buoyancy, the invisible force in every weighing Every object weighed in air is buoyed up by the air it displaces — roughly 150 parts per million of its mass for stainless steel at sea leve... Aug 5, 2026 VIM concept: the anatomy of a traceability chain 'Traceable to NIST' is one of the most-abused phrases in commerce. The VIM's definition (clause 2.41) is stricter and more useful: metrologi... Aug 4, 2026 Standards profile: ANSI/NCSL Z540.3 and the 2 % false-accept rule Z540.3 is the US national standard for calibration programs, and its most influential sentence is a probability: where calibrations include... Aug 3, 2026 Reading a balance like a metrologist: GMP 1 and turning points Before digital balances, reading a mechanical balance meant watching the pointer swing and averaging its turning points — and NIST's GMP 1 s... Aug 2, 2026 Inside SOP 4: double substitution, the workhorse of mass calibration Ask a mass laboratory how it actually compares an unknown weight to a standard and the answer, most of the time, is double substitution — th... Aug 1, 2026 Unified search now spans documents, definitions, standards and Q&A Search on Metrology Atlas now queries a single unified index covering the document library (page by page), the metrology dictionary, the sta... Jul 29, 2026 The 2019 SI redefinition, in practice: what changed for calibration laboratories Since 20 May 2019, all seven SI base units have been defined by fixing the numerical values of seven constants — the Planck constant now def... Jul 25, 2026 What your En number actually says — and what it does not Proficiency testing results for calibration laboratories usually arrive as an En number: the difference between your result and the referenc... Jul 22, 2026 Decision rules under ISO/IEC 17025:2017: guard banding moves mainstream The 2017 revision of ISO/IEC 17025 made decision rules explicit: whenever a laboratory states conformity, the rule that accounts for measure... Jul 21, 2026 ITS-90 in practice — and what the 2019 kelvin redefinition did not change Ask a calibration laboratory how it measures temperature and the honest answer is: against a scale, not a definition. The International Temp... Jul 19, 2026 Digital calibration certificates gather momentum The digital calibration certificate (DCC) — a machine-readable, cryptographically signed XML format pioneered by PTB and partners — continue... Jul 17, 2026 How to read a scope of accreditation before you buy a calibration An ISO/IEC 17025 accreditation logo on a website tells you a laboratory is accredited for something. Whether it is accredited for YOUR measu... Jul 13, 2026 A map of the GUM family: which uncertainty document answers which question 'The GUM' is shorthand for a whole family of JCGM documents, and knowing which member answers which question saves real time. JCGM 100:2008... Jul 8, 2026 150 years of the Metre Convention On 20 May 1875, seventeen states signed the Metre Convention in Paris, creating the International Bureau of Weights and Measures (BIPM) and... Jul 3, 2026 The Kibble balance: weighing mass against the Planck constant When the kilogram was redefined in 2019, the artifact in Sèvres gave way to a fixed numerical value of the Planck constant. The instrument t... Jun 27, 2026 Redefining the second: the road from cesium to optical clocks Since 1967 the SI second has been defined by a microwave transition in cesium-133. It is the most precisely realized unit in all of measurem... Jun 21, 2026 The VIM's fourth edition: what's changing in metrology's vocabulary The International Vocabulary of Metrology — the VIM — is the document that decides what words like calibration, traceability and uncertainty... Jun 16, 2026