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Knowledge from our laboratories for mass and force: weights and OIML classes, calibrating and checking scales, legal verification and the Dutch Metrology Act, force measurement and ISO 376, and what to do with a calibration certificate.

Weights and OIML R111 10 Knowledge about scales 7 Legal verification and legislation 4 Force measurement and force calibration 6 Certificates and quality 3

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Weights and OIML R111 Cast iron or stainless steel weights: which material suits your application? Cast iron, stainless steel or chrome-plated brass: the material of a weight determines which classes are possible, how much maintenance it needs and what it is suitable for. Knowledge about scales Checking your scale yourself between two calibrations With an interim check using a calibrated weight you spot a deviation in time. Read which weight to choose, how often to check, how to record it and what to do if the result is wrong. Legal verification and legislation The Dutch Metrology Act and scales: when is legal verification mandatory? When must a scale be legally verified, who supervises this and what must you do after a repair? A practical explanation of the Dutch Metrology Act for non-automatic weighing instruments, with a comparison with Belgium.

Weights and OIML R111

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Adjusting weights: how it works and when it is not possible If a weight falls outside its class, it can often be adjusted. This is how it works for knob, block and solid weights, and these are the alternatives when adjustment is not possible. Cast iron or stainless steel weights: which material suits your application? Cast iron, stainless steel or chrome-plated brass: the material of a weight determines which classes are possible, how much maintenance it needs and what it is suitable for. Conventional mass and air buoyancy in weights Every calibration certificate for weights states the conventional mass. What that convention means, why the air counts and when it makes a difference in practice. How often should you recalibrate weights? How to determine the interval No standard prescribes how often weights must be calibrated. This is how you determine a well-founded calibration interval yourself and recognise the signals to calibrate earlier. Measurement uncertainty on the calibration certificate of weights What does the measurement uncertainty on your weight certificate mean? An explanation of k=2, the one-third mpe requirement, the in-tolerance assessment and correction values. OIML R111 weight classes E1 to M3: tolerances and use The seven OIML R111 classes determine how much a weight may deviate. Read what each class means, what you use it for and find the complete tolerance table.

Knowledge about scales

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Calibrating, adjusting and verifying scales: the difference Calibration measures the error, adjustment corrects the scale and legal verification is the statutory inspection. See which operation you need and which misunderstandings are common. Checking your scale yourself between two calibrations With an interim check using a calibrated weight you spot a deviation in time. Read which weight to choose, how often to check, how to record it and what to do if the result is wrong. EURAMET cg-18 explained: tests, measurement uncertainty and report EURAMET cg-18 is the European guide for calibrating scales. We explain the three tests, the choice of test points, the measurement uncertainty and how to read a report. How often should you have a scale calibrated? There is no fixed period for calibrating a scale. Read who determines the interval, which factors play a part, when you need to calibrate earlier and how things stand for legally verified scales. Minimum weight of an analytical balance: explanation and worked example The minimum weight is the smallest quantity you can weigh out with sufficient accuracy. Read how it follows from the repeatability, how to calculate it and which environmental factors count. Using a crane scale safely and accurately Errors in crane scales are often caused by the way they are used. Read how to prevent swinging and shock loading, inspect lifting components and when calibration or legal verification is required.

Legal verification and legislation

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M mark, seals and accuracy classes: reading the type plate The type plate of a legally verified scale tells you whether it is verified, which class it falls into and for which range the verification applies. We explain the M mark, the seals, Max, Min, e and d with an example. Re-verification after repair: when is a new verification required? After a repair to the weighing system or a broken seal, the legal verification of a scale is no longer valid. Read which work this covers, how to approach the re-verification and how to combine it with a calibration. The Dutch Metrology Act and scales: when is legal verification mandatory? When must a scale be legally verified, who supervises this and what must you do after a repair? A practical explanation of the Dutch Metrology Act for non-automatic weighing instruments, with a comparison with Belgium. What is a Recognised Verifier and when do you need one? A Recognised Verifier verifies, marks and seals measuring instruments after recognition by the government. Read what that role involves, how it differs from a notified body and a calibration lab, and what to look for.

Force measurement and force calibration

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How often should a force gauge be calibrated? No law prescribes a fixed interval for force measuring instruments. Read how to determine a calibration interval on the basis of standards, use and history, and when you must recalibrate immediately. Hysteresis and repeatability in force measurement: what do they mean? The certificate of a force transducer states hysteresis, repeatability, reproducibility and zero return. Read what these terms mean, how they are measured and what you do with them. ISO 376 explained: classes 00, 0.5, 1 and 2 for force transducers ISO 376 divides reference force transducers into classes 00, 0.5, 1 and 2 on the basis of reproducibility, repeatability, interpolation error, zero error and hysteresis. Read what the classes mean and which one you need. Load cell calibration: just the sensor or the complete measuring chain? A load cell gives a signal in mV/V; only the readout turns it into a force. Read when to have the transducer calibrated on its own and when the complete measuring chain is the better choice. Mass, weight and force: what is the difference? A weight has a mass in kilograms, a scale measures a force in newtons and converts it back to mass. Read how mass, gravity, force and load cells are related and what that means for calibration. What is force calibration? From reference transducer to certificate A force calibration compares your force measuring instrument with a calibrated reference force transducer in the same line of force. Read how the measurement is performed, what tension and compression mean, which standards apply and what the certificate states.

Certificates and quality

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Calibration certificate explained: reading and assessing the results A calibration certificate shows how much your scale or weight deviates and how certain that statement is. Read which elements it should contain, how to assess the results against your own tolerances and what an auditor wants to see. ISO 9001, ISO 17025 and traceability: which certificate do you need? ISO 9001, ISO/IEC 17025 and traceability are often confused. Read what each term means and which calibration certificate you need in which situation. Measuring equipment management checklist: how to be ready for the audit A practical checklist to get your measuring equipment management for scales and weights ready for an audit: from register and intervals to certificates, interim checks and how to deal with nonconformities.
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