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The NIST Hybrid Humidity Generator (HHG) Laboratory provides calibration services for a variety of humidity–measuring instruments. Calibrations are performed by subjecting the instrument under test to air with an accurately known moisture content produced by the generator.
The HHG generates frost/dew points from –70 °C to +85 °C (mole fractions from 1×10E−6 to 0.57) using calibration gas flows up to 150 standard liters per minute. The HHG combines the two-pressure and divided-flow humidity generation techniques (hence the name "hybrid").
The calibrations may be performed using humidity definitions of dew/frost point, relative humidity, mole fraction, or mass ratio.
For the case of relative humidity calibrations, a separate calibration of the instrument's external temperature probe is performed by means of comparison against a standard thermometer. The instruments and ranges of calibration include but are not restricted to:
For dew/frost point temperatures, the uncertainty budget yields a total expanded uncertainty (k=2) of less than 0.025 °C for dew/frost point temperatures above –60 °C.
How to Arrange a Calibration
For contact information, shipping address, or cost of calibration, see Humidity Measurements.
100 Bureau Drive, M/S 8363