A transportable refractometer for assessment of pressure in the kPa range with ppm level precision

Abstract

A transportable refractometer for assessment of kPa pressures with ppm level precision is presented. It is based on the GAs MOdulation Refractometry (GAMOR) methodology, making it resistant to fluctuations and drifts. At the National Metrology Institute at RISE, Sweden, the system assessed pressures in the 4.3 - 8.7 kPa range with sub-ppm precision (0.5 - 0.9 ppm). The system was thereafter disassembled, packed, and transported 1040 km to Umea University, where it, after unpacking and reassembling, demonstrated a similar precision (0.8 - 2.1 ppm). This shows that the system can be disassembled, packed, transported, unpacked, and reassembled with virtually unchanged performance.

The Short-Term Performances of Two Independent Gas Modulated Refractometers for Pressure Assessments

“…As was alluded to above, to make viable assessments of large pressure shifts with short settling times, which is needed for a number of applications, it is of importance that the system has a fast response. Although several types of refractometers have been scrutinized over the years [ 3 , 4 , 5 , 6 , 7 , 8 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 24 , 25 , 26 ], virtually none of them has yet been assessed with respect to its short-term behavior. Access to two GAMOR-based refractometer systems allows for scrutiny of the short-term behavior of GAMOR-based refractometry in more detail.…”

Circular Comparison of Conventional Pressure Standards Using a Transportable Optical Refractometer: Preparation and Transportation

“…Although the response of this characterization was looking ostensibly linear on a pressure-vspressure plot, illustrated by Figure 4 (a), which shows the response of the TOP vs. the response of the pressure balance, a closer scrutiny reveals that the response is weakly non-linear. The solid curve shows a second order fit of the form 𝑎 + 𝑏 𝑃 + 𝑐 𝑃 2 , where 𝑎 = −0.614 Pa, 𝑏 = 1.0021, and 𝑐 = 1.52 × 10 −9 Pa −1 .…”

“…The refractometer has been jointly constructed by RISE and Umeå University (UmU), both in Sweden, and utilizes the Gas modulation refractometry (GAMOR) methodology [1]. This methodology reduces significantly the influence of various type of disturbances (primarily fluctuations and drifts), which makes the system extraordinary sturdy, and hence ideal as a transportable instrument [2].…”

‘Quantum-Based Realizations of the Pascal’: Status and Progress of the Empir-Project: Quantumpascal

“…The GAMOR methodology has also, thanks to its mitigation of the influence of various types of disturbances, made it possible to construct transportable systems [15], [16], [17]. A comparison between two GAMOR-based systems has demonstrated that the systems have an extraordinarily high short time precision, in the 10 -8 range [16].…”