The long and short of Swiss precision

A device for the 3-D measurement of micro-components used in industry METAS

Switzerland is a byword for precision. The Swiss national hero is William Tell, who at 80 paces hit an apple placed on his son's head with pinpoint accuracy.

His arrow would have taken about two seconds to hit the target; in today’s world scientists can measure the speed of light which travels nearly 600 million metres in that same time.

In Switzerland the Federal Office of Metrology (METAS) is the point of reference for everything to do with measurement. It provides the standard units, calibrates measuring instruments, and develops ever more accurate means of measuring.

Precise measurement is essential to modern life. Some examples are obvious: we expect the scales at the supermarket, the petrol pump, even the radar trap, to measure our fruit, our fuel or our speed correctly. Indeed, this is a legal requirement.

Manufacturers of such measuring equipment must get it certified by one of the bodies belonging to the Swiss Verification Service, run by METAS, before it can come onto the market. METAS also oversees the periodic checking of individual instruments – hundreds of thousands of them every year.

This consumer protection extends to areas which are less obvious. The environment is a growing cause for concern, which calls both for more research and new legislation. Neither is possible without accurate means of measurement. Harmful particles, noise pollution and electro-magnetic radiation all pose problems.

Pollutants in the air, in the form of particles only a few micrometres in size, are known to have an impact on both health and the climate, although much research remains to be done. METAS has developed a range of instruments to measure the size and concentration of these particles on an even smaller scale. It provides reference values for users all over Europe.

Underground labs

There can be few areas of life where METAS is not involved. It has 118 separate laboratories, many of them underground with their own separately controlled temperature and humidity. Some have special insulating walls and ceilings; some are so sensitive that the researchers do not enter them, but work on the results of their experiments on computers elsewhere in the complex.

METAS works closely with its counterparts in Europe and elsewhere in the world. Modern international trade cannot take place without agreed and reliable systems of measurement.

The European Union is Switzerland’s major trading partner. In the past few years Switzerland has been working to harmonise its regulations with EU legislation. As a result, instruments certified in Switzerland are acceptable throughout the EU and vice versa.

It is not only in legal matters that METAS cooperates with its counterparts abroad. One of the major challenges facing metrology today is to find an accurate definition of the kilogram.

The kilogram currently in use is defined in terms of a block of platinum-iridium alloy kept in Paris and agreed in 1889. It is the last unit of measure to be defined in terms of an artefact rather than a “natural constant”. (The metre, for example, is defined in terms of the speed of light, the second in terms of the behaviour of the caesium atom.)

METAS’ contribution to the international effort to define the kilogram is via a series of electro-mechanical experiments, using the Watt balance. The principle is highly complex; the challenge “difficult but exciting”, as the METAS researchers put it.

If and when they solve the problem, Switzerland’s copy of the Paris prototype kilogram, now kept carefully shielded from any outside influence under two bell jars, will be as much a museum piece as a mediaeval crossbow.

But for METAS the work continues. “There are no limits to accuracy,” says its director Wolfgang Schwitz.

swissinfo, Julia Slater

In brief

METAS, the Federal Office of Metrology, based in Wabern on the outskirts of Bern, is the point of reference for everything to do with measurement in Switzerland.

METAS has 118 specialised laboratories, with their own separately controlled temperature and humidity.

Its tasks include overseeing the certification of equipment such as weighing machines in shops, which are legally required to be accurate.

It cooperates with industry and universities in developing precise measuring equipment for industrial customers.

It houses the FOCS-1 atomic clock, accurate to one second in 30 million years.

It is responsible for providing standard measuring units, and houses the Swiss copy of the prototype kilogram.

It is engaged in the international search for a more accurate definition of the kilogram in terms of a natural constant instead of an artefact.