A Gas Pressure Scale Based on Primary Standard Piston Gauges

Area of Science:

• Metrology
• Pressure Metrology
• Gas Pressure Measurement

Background:

• The National Institute of Standards and Technology (NIST) previously defined its gas pressure scale.
• Advancements in metrology necessitate recalibration and redefinition of national standards.
• Accurate pressure scales are crucial for scientific research and industrial applications.

Purpose of the Study:

• To redefine the NIST gas pressure scale up to 17 MPa.
• To establish a new scale based on primary standard piston gauges.
• To ensure high accuracy and international comparability of gas pressure measurements.

Main Methods:

• Utilized two primary standard piston gauges (35.8 mm diameter) for the base scale (20 kPa to 1 MPa).
• Employed ten secondary standard piston gauges (Ruska 2465 type) to extend the scale to 17 MPa.
• Performed direct comparisons and elasticity theory calculations to determine effective areas, uncertainties, and gauge distortion.

Main Results:

• Achieved relative standard uncertainties of 3.0 × 10⁻⁶ to 3.2 × 10⁻⁶ for primary standards.
• Attained relative standard uncertainties as low as 4.2 × 10⁻⁶ for secondary standards at 300 kPa.
• Validated effective areas and uncertainties through international comparisons, showing agreement within expanded uncertainties.

Conclusions:

• The redefined NIST gas pressure scale up to 17 MPa demonstrates high accuracy and reliability.
• The new scale ensures consistency with international metrology standards.
• The results confirm the effectiveness of the primary and secondary standard piston gauge system.