The type plate of a legally verified scale carries the M mark. But who is permitted to verify such a scale again later, for example after a repair? In the Netherlands, this includes the Recognised Verifier (Erkend Keurder) under the Dutch Metrology Act: a company that has been granted recognition by the government to verify measuring instruments and then mark and seal them.
In this article you will read exactly what a Recognised Verifier does, how that role relates to a notified body and a calibration laboratory, and how to check whether a verifier is permitted to verify your instrument. If you want to know straight away how a re-verification works in practice, read more about verification and re-verification of a scale.
What does a Recognised Verifier do?
The Dutch Metrology Act stipulates that measuring instruments for certain applications, such as selling by weight, must be verified. The government does not carry out all those verifications itself. It can recognise companies that demonstrably have the knowledge, equipment and procedures to do so responsibly. Such a company is called a Recognised Verifier.
The work consists of three parts:
- Verifying: establishing whether the instrument meets the requirements that apply to its accuracy class, using calibrated weights that are sufficiently accurate.
- Marking: in the event of a positive result, affixing the required markings so that it is visible that the instrument has been verified.
- Sealing: closing off access to the adjustment and the weighing mechanism with seals, so that it can later be seen whether anything has been changed.
For scales, in practice this mainly concerns re-verifications: instruments that were previously verified and need to be assessed again, for example after a repair or a broken seal. A recognition is not unlimited. It has a defined scope, and the verifier must comply with the conditions attached to it. Supervision of legal metrology lies with the Dutch Authority for Digital Infrastructure (Rijksinspectie Digitale Infrastructuur, RDI).
Recognised Verifier, notified body or calibration lab?
Three parties are often confused. Each has its own role:
| Party | What does this party do? | When do you deal with it? |
|---|---|---|
| Notified body | Is involved in the initial conformity assessment of new instruments. The initial verification is carried out by the manufacturer or by a notified body. The body's number appears next to the M mark. | When purchasing a new verified scale. Usually the manufacturer or supplier arranges this. |
| Recognised Verifier | Re-verifies instruments that are already in use and affixes markings and seals. | After a repair, adjustment or broken seal. |
| Calibration laboratory | Measures the error of an instrument and records it with the measurement uncertainty in a certificate. This is not a legal verification. | For your quality system and audits. |
A calibration lab and a Recognised Verifier can be the same company, but they remain two different services. A calibration certificate does not make a scale legally verified, and a valid verification does not produce a calibration certificate. The difference between the terms is explained in more detail in calibrating, adjusting and verifying scales.
When do you need a Recognised Verifier?
You need a Recognised Verifier if a scale is used for a legally regulated application and the existing verification is no longer valid. The situations we encounter most often:
- work has been done on the weighing mechanism, for example replacing a load cell or weighing indicator;
- the scale has been adjusted and a seal had to be broken to do so;
- a seal is damaged or missing, even if this happened by accident;
- a check or calibration shows that the scale weighs outside the permitted error and adjustment is required;
- you take over a verified scale, for example when taking over a shop, and the seals are no longer complete.
If you weigh exclusively for internal use, such as production control or recipes, a legal verification is not mandatory. A calibration with certificate is then usually what your quality system requires. Which applications fall under the law is explained in the Dutch Metrology Act and scales. What needs to happen after a repair is set out in re-verification after repair.
How do you check whether a verifier is permitted to verify your instrument?
Not every verifier is permitted to verify every instrument. Therefore go through these points in advance:
- Ask about the recognition. A Recognised Verifier can indicate what the recognition covers. Ask for this in writing if you want to record it in your own administration.
- Provide the details of the instrument. Make, type, serial number, accuracy class and Max are on the type plate. A photo of the plate prevents misunderstandings.
- Have the verifier confirm that the verification is possible. A careful verifier checks this before the visit, not only on site.
- Ask which weights will be used. The weights must be calibrated and suited to the class and range of your scale. For a weighbridge, that also means sufficient weight and suitable equipment.
- Agree what you will receive afterwards. Think of the verification data and, if you wish, a separate calibration certificate.
If you are looking for general information on legal metrology, you can contact the supervisory authority, the RDI.
What happens during a verification?
A re-verification resembles a calibration, but the purpose differs. In a calibration you record the error. In a verification, the verifier decides whether the instrument meets the requirements for its class. Broadly speaking:
- the verifier checks whether the type plate is complete and legible and matches the instrument;
- the condition of the scale and its set-up are assessed, such as levelling, supporting surface and contamination;
- the scale is loaded with calibrated weights, at various points across the range and at various positions on the platform;
- where necessary, the scale is adjusted and then tested again;
- in the event of a positive result, the markings and seals are affixed.
If the scale does not comply, it does not receive new markings and may not be used for legally regulated applications. Adjustment or a repair is often the solution, followed by a new verification. How to recognise markings and seals is explained in M mark, seals and accuracy classes.
What we look out for in practice
Because we both calibrate and verify, we see both sides. A few experiences:
- Many scales that do not comply are not defective but dirty, not level or poorly positioned. A clean, unobstructed location saves time and prevents unnecessary rejection.
- Schedule a verification immediately after a repair. The longer a scale stands without a valid verification, the greater the chance that it will be used for charging customers anyway.
- Combine the verification with a calibration if your quality system requires a certificate. The weights are already in place.
- Record the verification in your measuring equipment register, with date and findings.
How MASSLAB helps you
MASSLAB is a Recognised Verifier and carries out re-verifications of verified scales, for example after adjustment or repair. Before every verification, we check on the basis of make, type and serial number whether we are permitted to perform the verification for that specific instrument. The initial verification of new instruments lies with the manufacturer or a notified body. Because we are also a calibration laboratory, verification and calibration can be done in a single visit. Read more about the procedure at scale verification and re-verification.