National Physical Laboratory

Are mercury barometers more accurate than non-mercury ones? (FAQ - Pressure)

The most accurate barometers are indeed the mercury primary barometers used at national measurement institutes such as the UK Primary Standard Barometer at NPL. 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.

Ten or more years ago it was still generally true that the long-term accuracy of a well-made and traditional Fortin or Kew Pattern mercury barometer was better than even the most expensive electronic barometer available. The electronic devices were easier to use, their electrical outputs could be interfaced to a computer and they did not, of course, contain hazardous mercury, but they needed considerably more calibration and maintenance to compensate for slowly drifting readings (poor reproducibility). With continual technological improvements over the years, however, it is certainly not true any longer and some of the best electronic barometers available now have comparable, and sometimes better reproducibility than the traditional mercury barometer.

Unless you particularly want to use a mercury barometer the use of a non-mercury instrument is recommended; they are smaller, more convenient, more adaptable, allow dramatically faster reading, safer and some are cheaper!

Last Updated: 25 Mar 2010
Created: 9 Aug 2007

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