Manufacturing Bits: June 28

Redefining the kilogram; measuring greenhouse gases.


Redefining the kilogram
The National Institute of Standards and Technology (NIST) has developed a new scale that could one day enable a new and improved definition of the kilogram.

The scale is called the NIST-4 watt balance. It has conducted its first measurement of a physical quantity called Planck’s constant to within 34 parts per billion.

The scale is not intended to alter the value of the kilogram, but rather it will remove an uncertainty in the official mass of the weight.

The NIST-4 watt balance (Source: NIST)

The NIST-4 watt balance (Source: NIST)

Meanwhile, Planck’s constant is the key to quantum mechanics. This is used to describe physics at the atomic scale. It also talks about how objects radiate energy. This is done using tiny packets known as quanta. Basically, Planck’s constant says the amount of energy is proportional to a very small quantity called “h.” The value of “h” is 6.62606983 x 10-34 kg∙m2/s, with an uncertainty of plus or minus 22 in the last two digits, according to NIST’s new scale.

With enough accurate measurements of Planck’s constant, researchers can make the value more precise. This, in turn, allows more accurate measurements of the kilogram.

NIST hopes to use its new scale to redefine the kilogram by 2018. But to get industry adoption, the system from NIST must pass some rigid tests. It must produce values with a relative standard uncertainty of no more than 50 parts per billion, and one with no more than 20 parts per billion. All these values must agree within a statistical confidence level of 95%.

The first results with the scale were promising. “This measurement was essentially a dry run,” said NIST physicist Stephan Schlamminger. “We were hoping to achieve an uncertainty of within 200 parts per billion by this point, but we got better fast.”

Measuring greenhouse gases
The Fraunhofer Institute for Applied Optics, the German Aerospace Center (DLR) and the European Space Agency (ESA) have developed a more efficient way to measure greenhouse gases in the environment.

Researchers have devised a new way to integrate two components–prisms and gratings—thereby achieving a new level of quality for spectral resolution.

The technology solves a major problem. Today, spectrometers are launched into space via satellites. These instruments measure the amount of greenhouse gases in the air by analyzing light.

The light is dissected into its component colors. To accomplish this, the instrument incorporate prisms and gratings. Prisms deflect blue light. Gratings deflect red.

The problem? It’s difficult to combine these structures. Adhesives won’t work. They absorb light, which would distort the measurements.

To combine these elements, researchers used another technology. Researchers used a technique called hydrophilic bonding. Oxygen and hydrogen atoms are bonded to the wafer’s surface.

A prism and grating structure (Source: Fraunhofer IAO)

A prism and grating structure (Source: Fraunhofer IAO)

“We combine the optical elements with each other at the atomic scale, namely via oxygen bridges,” said Gerhard Kalkowski, scientist at the Fraunhofer Institute. “In this way, we will provide the key for high-resolution systems made of prism-grating structures to also be able to be used in space in the future.”


Timothy Reeves says:

“Prisms deflect blue light. Gratings deflect red.”


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