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- The density of a solid or liquid may be fundamentally determined by hydrostatic weighing using Archimedes' principle.
- The mass of a body relates to the amount of material it contains and there is no difference between mass and true mass. When a weight is calibrated the mass value quoted on its certificate of calibration is normally a conventional mass value - appropriate where the value is determined by weighing the item in air.
- Force is a measure of the interaction between bodies, mass is a measure of the amount of material in an object, weight is the gravitational force acting on a body (although for trading purposes it is taken to mean the same as mass) and load usually means the force exerted on a surface or body.
- The Rugby radio station, with call-sign GBR, was brought into service in 1926 by the Post Office as a telegraphy station with world-wide coverage and a frequency of 16 kHz.
- As UTC is running about one second per year faster than time based on the Earth's rotation (Greenwich Mean Time, or Universal Time), an extra second is occasionally inserted in the UTC time scale to let it fall behind and start catching up again.
- Instrument calibration is often thought to be expensive but the information contained in the resultant certificate is usually worth considerably more. This is not always appreciated and, on receipt, many certificates are wastefully consigned to drawers, shelves or even wall plaques.
- GPS has its own date and time scale for expressing satellite positions, based on counting weeks, and seconds within a week. To limit the size of the numbers used in the data and calculations the GPS Week Number is a ten-bit count in the range 0-1023, repeating every 1024 weeks.
- There are many different types of barometer but they fit into two broad categories - those containing mercury and those that do not.
- The following is a list of manufacturers and distributors ...
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- There are three main options available for calibrating a force measuring system and establishing its measurement uncertainties.
- The International Temperature Scale of 1990 goes down to 0.65 K, below this, to 1 mK, is the Provisional Low Temperature Scale of 2000 (PLTS-2000).
- NPL offers a cost-effective re-certification service after the initial certification period has expired.
- Machines capable of undertaking force calibrations are known as force standard machines and they may be categorised as either primary or secondary.
- GPS has its own date and time scale for expressing satellite positions, based on counting weeks, and seconds within a week. To limit the size of the numbers used in the data and calculations the GPS Week Number is a ten-bit count in the range 0-1023, repeating every 1024 weeks.
- A millennium is any period of a thousand years. So you could say that the next millennium begins now. The third millennium of the Christian Era began at the start of the year 2001 A.D.
- The gigasecond is the only scientifically-preferred time interval that is passed in adult life.
- There are no 'official' definitions of the duration of spring, summer, autumn and winter for civil purposes. Many bodies, for example meteorologists, adopt a convention for the purpose of presenting statistics by grouping the twelve months of the year into four three-month seasons.
- The International Earth Rotation and Reference Systems Service (IERS), based at the Paris Observatory, announces twice yearly whether or not there will be a leap second at the end of the following June or December.
- The UK National Standard Kilogram is kept in a basement vault at NPL. It is stored in an air-tight enclosure, only exposed to the air via two micropore filters.