A primary pressure pattern

The system allowed Spain to become an international reference in terms of pressure measuring

Did you know that IK4-TEKNIKER delivered the world’s most accurate pressure pattern to Centro Español de Metrología (CEM) (the Spanish Metrology Centre)?

The technology centre designed and developed a primary pattern to measure absolute pressures and validating all pressure measurements in Spain in 2009 for the Spanish Metrology Centre.

To achieve this goal, the technology centre worked on a model that used a double mercury column operating according to the primitive experiment by Torricelli.

The mechanism consisted in inserting perfect fluid inside a U-shaped pipe. Once the pressure settings applied at each end of the pipe differ in a (DP) value, it means there is a difference in height between them.

The result is expressed via the formula DP = r·g·h, in which “r” is liquid mass density, “g” stands for local gravity accelerations and “h” is the difference in height.

Based on the veracity of the formula, and once a vacuum has been created at either end, the DP value provides a measurement of absolute pressure.

The empirical application of this simple physical principle, however, gave rise to multiple execution challenges due to the very low level of uncertainty required by the equipment to become the national pressure pattern.

Some of the challenges that researchers at the technology centre had to cope with were related to measuring the height of mercury columns with laser interferometry and a compensation tracker, to the purity of mercury (99.99999%), to uniform temperature monitoring below 0.01 ºK and total vibration insulation provided by special foundations.

Once the above mentioned obstacles were overcome, researchers built a “barometer” capable of measuring maximum 3 bar absolute pressures with a level of uncertainty below + 0.5 Pa, the most accurate of the world at that point in time.

The new barometer became a reference to compare pressure measurements of equipment in a number of fields such metrology, airplane altimeters, vehicle tyre pressure levels or domestic gas cylinder settings. Relevant applications were also developed in the industrial environment, particularly in vacuum processes.