A platinum resistance thermometer is a piece of platinum wire which determines the temperature by measuring its electrical resistance. It is referred to as a temperature sensor and offers an excellent combination of sensitivity, range and reproducibility. Platinum resistance thermometers are a common way to measure the temperature over a wider range of temperatures – used in applications from industry to weather stations. NPL calibrates the thermometers to make sure they are as accurate as possible.
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Find out more about measuring the temperature of the earth
Accurate mass and length standards
The stability, both chemically and physically, of platinum means that is can be used as a ‘standard’ which other objects can be compared with. The kilogram used to be defined using a single standard weight made of platinum-iridium alloy.
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In 1875 the Metre Convention was signed by participating nations and the International Bureau of Weights and Measures (BIPM) was established.
In 1880 three platinum-iridium standard weights were manufactured from material provided by the British firm Johnson-Matthey. One of these weights was selected as the master kilogram (Le Grand K). Further copies, calibrated against Le Grand K, were manufactured in 1889. By the same year a number of platinum-iridium metre bars had been produced, and one was then selected as the International Prototype metre. Certified, calibrated copies of both the kilogram and metre were distributed to the member countries of the Metre Convention. Lots were drawn and Britain received kilogram number 18 and metre bar number 16.
Find out more about SI units
The candela is the SI unit for measuring the visual intensity of light sources, such as light bulbs or torches. In the past, the unit used to measure visual intensity was called the candle, however this lacked sufficient accuracy and reproducibility. A new standard, proposed in 1937, and ratified in 1948, was based upon a perfect ‘black body’ at the freezing point of platinum and gave the name ‘candela’ to the unit of luminous intensity.
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Platinum particles in the air
NPL is actively researching measurement techniques for polluting airborne particles, particularly metal particles including platinum. We provide services and give advice to companies and researchers to help them understand how to make measurements and understand the results.
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Platinum as a powerful magnet
Cobalt-platinum permanent magnets are quite exceptional. They are one of the most powerful permanent magnetic materials available and are readily fabricated. They are used in miniaturised circuits where space is limited and can be made into strips or wires. NPL calibrates cobalt-platinum magnets to ensure they work effectively.
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