Studies have been carried out of the effects of using
three different cleaning methods on 1 kg stainless steel mass
standards, all three methods being suitable for use in a mass
calibration laboratory. The methods investigated were manual
and ultrasonic cleaning using solvents, and boiling in pure
water. Boiling in pure water proved the most effective and
additionally produced the most stable weights with stabilities
of better than 1 part in 108 over a period of months.
Ultrasonic cleaning was almost as effective as boiling but the
weights were less stable after the cleaning process. Manual
cleaning proved the least effective and the mass change
produced was very dependent on the specific cleaning technique.
Finally, a summary of the key features of each cleaning
technique is given.
The measurement of pressure above atmospheric pressure relies in many cases on the use of piston-cylinder assemblies, often called piston gauges or pressure balances. One of the major limitations to the measurement uncertainty with which it is possible to realize the pascal is lack of knowledge of how the piston-cylinder assembly distorts as it becomes pressurized. The feasibility of directly measuring such distortion by monitoring the change in the electrical capacitance between the piston and cylinder as the system is pressurized has been demonstrated.
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