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Answers to the most popular questions about NPL and our activities.
NMIs realise, maintain and develop their country’s primary measurement standards.
Both are fundamental to human activity, but what’s the difference?
The meaning of 12 am,12 pm, midday, midnight and the 24-hour clock
When used in measurement it is vital to use the correct word
There are no official definitions of the duration of spring, summer, autumn and winter.
Atmospheric pressure reduces with altitude for two reasons, both of which are related to gravity.
Both are used to describe mass and to compare substances
What can you do to ensure you receive the correct time?
The definition of a vacuum is not precise but is commonly taken to mean pressures below, and often considerably below, atmospheric pressure.
The term g-force is used to convey values of force and acceleration.
Historically, there have been a variety of units of force and conversion factors.
We use these words on a daily basis, but do you really know the difference?
Air density can be measured in two broad categories
There is no simple formula for converting between dew point and relative humidity.
Both devices measure pressure, but what’s the difference?
All objects at temperatures above absolute zero emit thermal radiation.
A platinum resistance thermometer (PRT) contains a piece of platinum wire, whose electrical resistance is proportional to temperature.
The card requires a powerful microscope just to see it
Want more detail? Delve into the subjects more deeply.
The SI units
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