Automated Piston Gauge Calibration System.

Piston gauges or pressure balances are important primary standards for the realization of the SI unit of pressure, the pascal. Because of their long-term stability, they are also used as secondary or working standards in the dissemination of the pressure scale. The National Institute of Standards and Technology (NIST) operates and maintains a calibration service for these devices, and has recently undertaken a modernization effort. Following a preliminary investigation into the feasibility of using transducers as instantaneous in-situ transfer standards, we now present the results of a near fully automated calibration system. This effort includes the design, building, and validation of an automated gas-handling manifold, and the development of a new software suite. The new system demonstrates an expanded uncertainty on the order of 1 in 105, comparable to the traditional system, but offers a five-fold decrease in calibration turnaround time.

Fiber Bragg Grating Based Thermometry.

In recent years there has been considerable interest in developing photonic temperature sensors such as the Fiber Bragg gratings (FBG) as an alternative to resistance thermometry. In this study we examine the thermal response of FBGs over the temperature range of 233 K to 393 K. We demonstrate, in hermetically sealed dry Argon environment, FBG devices show a quadratic dependence on temperature with expanded uncertainties (k=2) of ≈500 mK. Our measurements indicate that the combined measurement uncertainty is dominated by uncertainty in determining peak center fitting and thermal ageing of polyimide coated fibers.