Pressure
NPL hold the UK’s pressure standards.
Pressure Calibration Services exist for the calibration of:
- Barometric pressure measuring devices.
- High-pressure measuring devices and pressure balances.
We offer consultancy services, including the design and manufacture of primary pressure standards for other laboratories, and an enquiry service for pressure and vacuum measurement-related issues. We also run a pressure and vacuum measurement special interest group within EMAN (the Engineering Measurement Awareness Network) called Pressmet, which is for the benefit of instrument end users, manufacturers and academics.
Representing the interests of the UK, we are active participants in a number of international projects under the auspices of EUROMET and the Consultative Committee for Mass and Related Quantities (CCM) of the Bureau International des Poids et Mesures (BIPM).
Pressure products & services
Pressure units
- No, they are not. The internationally recognised SI unit for pressure is the pascal, abbreviated to Pa, and this is the unit realised by the primary measurement standards in the world's national metrology institutes to provide traceability for pressure measurements.
- The most accurate barometers are indeed the mercury primary barometers used at national measurement institutes. Most barometers, though, are secondary instruments rather than primary ones and when considering these it is not correct to say that those based on a mercury column are invariably more accurate than those that are based on an alternative principle.
- Yes it can in some circumstances but, where it does, it is fairly easy to ensure that its effect on the measurement uncertainties obtained is negligible.
- When converting between pressure units consideration should be given to the number of significant figures to use, bearing in mind that many of the underlying conversion factors are not themselves exact and cannot be made so.
- To calculate a pressure value using a liquid column - for example a mercury barometer - or a pressure balance it is necessary to know the gravitational acceleration at the location of the instrument. It can be determined by measurement on site, calculation or interpolation of measured values.