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Thermodynamic Metrology Group

Welcome
Temperature and humidity thumbnailThe Thermodynamic Metrology Group realizes, maintains, and disseminates the national measurement standards for temperature, humidity, pressure, vacuum, and leaks. The Group advances thermodynamic measurements and applications; calibrates sensors and disseminates practical standards; participates in international comparisons to validate national standards; develops measurement methods, devices, and reference materials and data; assists users in the assessment of measurement uncertainty; prepares and promulgates evaluations and descriptions of measurement processes; coordinates national and international measurement standards and methods; and determines the uncertainty of the national standards with respect to fundamental thermodynamic definitions.
Programs/Projects

Humidity—The NIST Thermodynamic Metrology Group maintains and develops national standards of humidity (in the range 1 nmol/mol to 0.6 mol/mol of water concentration), and supports calibration of all types …

Hybrid Humidity Generator—NIST's new primary standard humidity generator, the Hybrid Humidity Generator (HHG), replaces the NIST 2-Pressure Humidity Generator, Mark 2 (2-P). The HHG produces humidified air of known moisture …

Johnson Noise Thermometry—Johnson noise thermometry (JNT) is a primary temperature measurement technique based on the fundamental properties of thermal fluctuations in conductors. We measure these fluctuations with respect …

Thermometry—The NIST Thermodynamic Metrology Group maintains and develops national standards of temperature (in the range 0.65 K to 1235 K), and supports calibration of all types of contact thermometers up to …

Acoustic Thermometry—By measuring the speed of sound in argon gas, we have determined thermodynamic temperature with unprecedented accuracy in the range 0 °C to 552 °C. Our results are used to improve the accuracy of …

Pressure—The NIST Thermodynamic Metrology Group (TMG) provides critical research into pressure measurement capabilities improving uncertainties in user facilities and developing new national standards. …

Dynamic Pressure—Manufacturing processes by their very nature require a judicious, time-dependent use of pressure and temperature to transform a base material into a valuable commodity. Modern manufacturing with …

Realizing Pressure, Temperature, and Length using Optical Interferometry—This project aims to fundamentally change the methods for realizing and disseminating the SI units of pressure, temperature, and length. The underlying metrology behind these advances is the …

Spectroradiometry of sources—Calibration standards for spectral radiance and spectral irradiance are disseminated in the form of transfer lamps and integrating sphere sources. These disseminated standards are made traceable to …