Distinguishing Thermal Fluctuations from Instrumental Error for High   Pressure Charged Gas
  Thermodynamic parameters such as temperature and pressure can be defined from the statistical behavior of a system. Therefore, thermal fluctuation is an inseparable characteristic of these parameters which eventually finds its way into experimental data. Analyzing these fluctuations is very useful in studying the phase transitions of a physical system or its behavior around critical points. However, this approach is not straightforward as most of the times it is impossible to distinguish meaningful thermal fluctuations from those due to the instrumental errors. In this article, we have offered a method by which an experimenter can separate this multi-sourced fluctuation into its constitutive parts according to their sources. Although the article is only focused on a specific system, which is a high pressure charged gas, we have used a computational method which could be used for various other systems. Our proposed idea is very efficient and reduces the required computation time by a remarkable fraction. We have used Euler algorithm, which generally does not hold the internal energy conserved; But we have used this fact as a tool which allows us to surf in the phase space of the system and reach different energy levels in significantly less time. Although system does not spend enough time in a single energy level to equilibrate, but we have been able to extract the details of the equilibrium state out of our data. Using numerical computations combined with theoretical modelings we have given a final expression for the amount of the overall fluctuations existing in the measured pressure values. This expression is given in terms of the characteristics of both the gas and the barometer so that it can be experimentally verified. 
Alek Bedroya, Mahmud Bahmanabadi
physics.comp-ph