Centre Spanish of Metrology: the central reference

In the field of dimensional metrology, and all other measures are in the world, each country (see specific section) has a National Institute that operates as a centre of reference. In Spain, this body is the Spanish Center of metrology, which boasts a unique facility in Madrid that, already from his architectural approach, is ready to measure. Not only that: referencing.

Center Spanish of Metrology (CEM) is an autonomous body under the Ministry of Promotion, created by Royal Decree 415/1985, of 27 March, in pursuance of provisions of law 3/1985, of 18 March, metrology.

This law establishes the legal framework which is develop all the metrological activities in Spain, and was enacted with three basic objectives:

• Defining legal units of measurement and establishing chains officers of calibration in order to relate and to rank all the measure patterns existing in our country.
• Establish the metrological State on the instruments of measure, in order to ensure the correctness and accuracy of the measures in defense of citizen safety and health, avoiding fraud in detriment of consumers.
• Unify activity metrology in Spain through the creation of a National Center of metrology

The EMF is the institution responsible for the Spain Metrology Organization and its powers established by law 31/1990 of December 27, are the following:

• Custody and maintenance of national standards of units of measure.
• Establishment of the calibration official channels.
• Exercise of the functions of the General Administration of the State in field of legal metrology.
• Projects of research and development in the field metrological.
• Training of specialists in metrology.

To carry out these tasks there is some facilities and labs that are located in the town of three Cantos (Madrid), in which 120 people work.

The EMF represents Spain before the metrological organisations international and maintains close cooperation with the agencies national and international metrology-related.

As regards the distribution of competences between the Applies to Directors-General of the State and the autonomous communities, that article 149 of the Spanish Constitution attributed to the State, between others, exclusive competence to legislate in respect of weights and measures and to determine the exact time, while the various autonomous communities they have assumed executive power and control of market in the field of legal metrology.

Area of Length of the CEM

Corresponds to the area of Length the achievement and maintenance of the national pattern of the unit of length, the meter, and the national pattern of the unit of plane angle, the radian, unit of the above, both belonging to the System SI (SI), declared legal system in Spain according to Law 3/1985, of metrology.

Also corresponds to the spread of both units by calibration patterns, instruments, equipment and systems for measuring of lower level, by giving them the necessary traceability.

Area length annually a large number of calibrations of high level, which are extensively woven industrial and research in our country, due to the multiplier effect derived from the hierarchical scheme Metrology is based on that.

Although most of the work have to do with scientific metrology and applied, the area is also responsible for legal metrology to part It affects those length measuring instruments subject to control metrological.

A very important part of the activities focused on the establishment of new and improved methods of measurement, looking for the less uncertainty, the What happens in most cases by the automation of the processes. All measurement and calibration procedures used meet the requirements imposed by the quality system of the EMF, being subject to periodic review.

For the fulfillment of all these missions, the area is divided five laboratories:
Primary lengthof Dimensional Metrology, of measurements Angular, Control forms and quality surface.  

Primary laboratory of length

He performed and maintains the national pattern of the unit of length, the metre. The metre is defined since 1983 (17TH GFCM, res.) 1) as the length of the path travelled by light in vacuum during a time of 1/299 792 458 s.

The national pattern of length consists of a monochromatic radiation of coherent light value of frequency has been established by the Committee International weights and measures, whereas for the speed of light in the empty constant value 299 792 458 m/s.

The conservation of the pattern is performed with helium-neon lasers stabilized on a component of the hiperfina structure of the transition 11-5 R (127) of the 127 iodine molecule, whose length of wave in a vacuum (633 nm) has a typical relative uncertainty of 2.5 x 10E-11 according to recommendation 3 (CI-1992) of the International Committee of Weights and measures.

In this laboratory is also the dissemination of the unit, through calibration of lasers and laser interferómetricos systems. In addition determine wavelength of the issuer and its stability, determines the measurement error of the system by comparison with a similar system in the lab, over a distance of 25 m. The sensors of pressure and temperature of the system, used to determine the value of the index of refraction of air, and thus know the value of the wavelength issued under ambient conditions, they measured the Pressure laboratory the Area of mass and in the Area of temperature, respectively.

Dimensional metrology laboratory

In this lab continues the spread of the unit long until the first pattern materialized high-level, both "a song" (block pattern) as "strokes" (rules for) (strokes). These patterns are the reference of other laboratories of calibration, either an integral part of equipment and measurement systems.

The laboratory has high precision measurement equipment (ground-based interferometers, comparators, etc.), some of them designed and built entirely in our country, which has a capacity of measurement has been demonstrated after the participation in comparisons ring.

A specific section of the laboratory is dedicated to the Machines of Coordinate measurement where, in addition to calibrations for the outside, develop new methods for calibration of own machines, that it can be applied to the industry.

This laboratory expected soon with a new section dedicated to the Nanometrología, in collaboration with the laboratory of surface quality, where new types of measurements consistent with technology needs are addressed Today, such as the determination of wider track, line spacing, in one and two dimensions, globally, the assessment of height of layer deposition processes and lithographic, etc.

 

Angular measurements laboratory

This laboratory keeps the unit of plane angle the radian, derived from the length through quotient (method within or method) (tangent), either generated in an absolute way through subdivision of the circle in a number of angles in the Centre, taking into account the property that the sum of all of them necessarily is 360 °.

The laboratory has an angular generator absolute, with 360 degree field with resolution of 0.04 ", and uncertainty of up to 0,1". Also has optical and mechanical generators, with photoelectric autocolimadores high-precision. Among the regular calibration of rotary tables, patterns angular, autocolimadores and optical polygons.

There is also a section devoted specifically to the calibration of instruments topographical, mostly collimators and Theodolites.

Forms control laboratory

The laboratory of Control forms evaluate defects patterns of high level and in parts of big finish. With the help of a team specially developed measurement for this laboratory is to the determination of defects of righteousness, parallelism, roundness, cylindricity and perpendicular, among others.

The laboratory has a section for the determination of Flatness by optical methods. Using a type Fizeau Interferometer is It controls the flatness of flat and plano-paralelos, flat glass used in interferometry, expensive measure of realization patterns (longitudinal and angular blocks, optical polygons, etc.). The pieces to measure can have diameters of up to 150 mm, and can be of any between 4% and 99% reflectivity material. The measurement can be through the evaluation of static patterns of interference fringes, or well using phase shifttechnique. For high mesurandos quality can reach up to 0.01 µm uncertainties.

Laboratory of surface quality

This lab examines samples of different types of materials, characterizing the surface finish of them by medium standard roughness parameters. Obtaining these parameters It is performed using the method of the profile, surface roughness measuring equipment using probes with different radii of tip, in contact with the piece. It also probes without contact, diode laser, that analyze the surface under study through analysis of the reflected light by it.

Laboratory calibrates each year dozens of patterns of roughness and patterns of amplification, used to adjust the response of the surface roughness measuring equipment. The calibration of the latter, consisting of grooves or steps in different ways, is done by means fixation microscopy. The microscope of laboratory You can work with white light or monochromatic light, and can evaluate static patterns of interference fringes, either use the technique of phase shift. The use of one or another type of light or technique It depends on the nominal value, step and topographical characteristics, roughness and reflectivity of the sample.