NIST scientists have developed a new pressure measurement instrument called the Fixed Length Optical Cavity (FLOC), which operates as a primary standard based on quantum-chemistry calculations. Created in partnership with industry, this device offers 35 times higher precision than traditional mercury manometers and has been miniaturized to a portable 2.5 cm size. The technology works by comparing the speed of light in a vacuum to its speed through a gas, using the ratio to determine pressure. Because it relies on fundamental physical constants rather than physical calibration, the instrument does not require periodic recalibration at NIST.
The system requires knowing the inherent refractive index of the gas, which NIST is also developing methods to measure using a Variable-Length Optical Cavity (VLOC). This quantum-based approach eliminates the need for mercury, which is being phased out globally. The design is intended to replace high-end mercury manometers in industrial settings where precision is critical.
This technology impacts various large-scale applications, including petroleum refining, aerospace, and microchip manufacturing. It can be used to make direct pressure measurements or to calibrate instruments that track liquid flow and other properties. The shift toward this optical standard supports safer and more accurate industrial processes without the limitations of bulky or toxic equipment.
Source: https://www.nist.gov/noac/technology/thermodynamics/pressure
Keywords: Fixed Length Optical Cavity, optical refractive index, photonic manometer
