Uncertainty Budget for the NIST Hybrid Humidity Generator
Christopher W. Meyer, W Wyatt Miller, Dean C. Ripple, Gregory E. Scace
We provide here a detailed uncertainty budget for the new Hybrid Humidity Generator (HHG) that has been constructed at the National Institute of Standards and Technology (NIST). The HHG generates frost/dew points from 70 °C to +85 °C using calibration gas flows up to 150 L/min. For frost/dew points above 15 °C, the two-pressure method is employed, and for frost points at or below 15 °C, the divided-flow method is used (hence the name hybrid). The total expanded (k=2) uncertainty is estimated for HHG generation of the following quantities: frost/dew point, mole fraction, and relative humidity. The total uncertainty is estimated separately for the two-pressure and divided-flow methods.