Characterization of a static expansion standard for calibrating medium and high vacuum pressure gauges

The Centro de Desarrollo Tecnológico del Gas developed a static expansion system to enable the calibration of medium and high vacuum pressure gauges in Colombia. The system can generate pressures between 0.1 Pa and 100 kPa. The characterization tests included the evaluation of pressure stability and desorption rate, a trueness test, and the analysis of the uncertainty budget of the calibration result. The pressure stability test was successfully completed and showed the positive effect of baking on the final pressure in the system. The trueness test allowed concluding that the calibration results with the system are comparable with those obtained with a reference meter traceable to a national metrology institute. The uncertainty budget analysis indicated the dominance of the pressure of the unit under calibration and of the initial pressure in the small tank in different pressure ranges on the uncertainty of the result. A comparison with a Monte Carlo simulation led to the conclusion that in this situation, the GUM (Guide to the Expression of Uncertainty in Measurement) method is not ideal for estimating the uncertainty of the results.