Novel system may help redefine International unit of temperature

June 4th, 2008 - 3:53 pm ICT by ANI  

Washington, June 4 (ANI): Researchers at the National Institute of Standards and Technology (NIST) have built a new system that may help redefine the International unit of temperature.

The system relies on the noise of jiggling electrons as a basis for measuring temperatures with extreme precision.

It is extremely precise in part because it is based on the predictable quantum effects of superconducting elements located between the dashed slits on the top and bottom of the chip .

The system is nearly precise enough now to help update some of the crucial underpinnings of science, including the 54-year-old definition of the Kelvin, the international unit of temperature.

NISTs Johnson noise thermometry (JNT) system represents a five-fold advance in the state of the art in noise thermometry thanks to its use of a unique quantum voltage source combined with recent reductions in systematic errors and uncertainty.

It is also simpler and more compact than other leading systems for measuring high temperatures, such as those based on the pressure and volume of gases.

Whats beautiful about our JNT system is that its so conceptually simple, said project leader Sam Benz. All the measurements are electricalthey dont require large volumes of gas and mechanical systems that change in different environmental conditions, he added.

As a thermometer, the JNT system will be most useful in the range from approximately 500 K (227 degrees C or 440 degrees F) to 1235 K (962 degrees C or 1763 degrees F).

Though its most obvious application is as a primary measurement standard (maintained at NIST and other national metrology labs for calibration of thermometers), but it also might be used directly in some industrial thermometry labs.

The recent JNT improvements are especially significant because they may contribute to a separate important measurement problem, the determination of Boltzmanns constant.

Several years from now, the international metrology community is expected to fix the value of the Boltzmann constant, used in scientific calculations to relate energy to temperature in particles.

The Boltzmann constant, in turn, would then be used to redefine the Kelvin as part of an international effort to link all units to fundamental constants, a more stable and reproducible approach than traditional measurement standards based on physical objects or substances.

According to Benz, the JNT system is the only electrical approach to determining the Boltzmann constant, and is currently among the top three thermometry systems competing for the redefinition, in terms of offering the lowest uncertainties. (ANI)

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