Companies need to ensure that the results they obtain from their measuring equipment are correct when used in key activities such as controlling process variables, assuring the quality or safety of their products, processes or services, or obtaining data required for analysis and important decisions.

Component ageing, temperature changes, the mechanical stress supported by the equipment, etc. lead to the gradual impairment of its functions. When this happens, measurements and tests become less accurate, which affects both the design and quality of the product.

It is therefore essential to have technically competent calibration services to meet the metrological needs of companies, which are increasingly more diverse and technologically complex. Accredited laboratories are the only ones that guarantee the traceability and reliability of calibration results.

Accredited laboratories cover all areas of calibration (electricity, mechanics, temperature, optical, dimensional, etc.) for a wide range of variables and equipment, from more "traditional" or "common" – weighing instruments, presses, electrical gauges, etc. to more specific or innovative –video signals, thermometric cameras, exhaust emission analysers and fibre optics– to provide services to all types of industry.

 

State metrological control is applied to measuring equipment or systems that can affect the transparency of commercial transactions, health or consumer and user safety and the environment.

These are some measuring systems and devices that are subject to this control: those used in the control of basic supplies (water, gas and electricity meters or fuel dispensers), weighing instruments, taximeters, slot machine counters, those used in road safety controls (vehicle roadworthiness or speed cameras to control vehicle speed) or temperature recorders and thermometers used in the transportation, storage and distribution of refrigerated foods, among others.

Public authorities, in their respective areas of competence, are responsible for their designation and they use the ENAC accreditation tool as assurance of their technical competence.

In Spain, there are three types of conformity assessment body for legal metrology: Notified Bodies, Metrological Control Bodies and Authorised Metrological Verification Bodies. The first two of them are about the commercialization and putting into service of the equipment while the latter does so for equipment that is already on the market or for instruments in service.

At this stage, the organisation responsible for product conformity (usually the manufacturer) selects the applicable conformity assessment module/s and instructs a Notified Body or Metrological Control Body to assess the conformity of the measuring instrument with the applicable essential, technical and metrological requirements. At this point, seals to prevent access to certain parts of the measuring instrument are attached to avoid tampering.

Once the instrument is in operation, it must be checked periodically or after repair or modification to confirm that it reads measurements correctly and that its measurement errors are lower than the maximum permissible errors. If the instrument passes the check, a "conforms” label is attached; if not, a red label is attached disqualifying it for service.