Fig. 1.
Fig. 2.
Fig. 3.
Fig. 4.
Fig. 5.
Fig. 6.
Fig. 7.
Uncertainty budget at −10 °C dew point temperature_
| Source | Value | Distribution | Divisor | Sensitivity coefficient | Standard uncertainty |
|---|---|---|---|---|---|
| Repeatability SPRT | 0.001 | Normal | 1 | 1 | 0.001 |
| SPRT calibration | 0.003 | Normal | 2 | 1 | 0.0015 |
| SPRT resolution (indicator unit) | 0.001 | Rectangular | 3.46 | 1 | 0.000289 |
| Bridge calibration | 0.0001 | Normal | 2 | 2.6 | 0.00013 |
| Bath stability | 0.01 | Rectangular | 1.73 | 1 | 0.00578 |
| Bath homogenity | 0.01 | Rectangular | 1.73 | 1 | 0.00578 |
| Saturator efficiency | 0.106 | Rectangular | 1.73 | 1 | 0.06127 |
| Dew-point hygrometer calibration | 0.06 | Normal | 2 | 1 | 0.03 |
| Resolution of hygrometer | 0.01 | Rectangular | 3.46 | 1 | 0.00289 |
| Combined uncertainty | 0.069 | ||||
| Expanded uncertainty (k = 2) | 0.14 |
Measurement results_
| No. | Saturation temperature t(SPRT) [°C] | Measured value of the hygrometer t(CMH) [°C] | Difference Δt = t(SPRT) –t(CMH) [°C] | Extended uncertainty [°C] |
|---|---|---|---|---|
| 1 | −50.074 | −49.63 | −0.444 | 0.52 |
| 2 | −40.077 | −39.83 | −0.247 | 0.29 |
| 3 | −30.058 | −29.96 | −0.098 | 0.13 |
| 4 | −20.025 | −19.95 | −0.075 | 0.11 |
| 5 | −10.076 | −9.97 | −0.106 | 0.14 |
| 6 | 0.034 | 0.05 | −0.016 | 0.06 |
| 7 | 10.006 | 9.92 | 0.086 | 0.12 |
| 8 | 20.008 | 19.91 | 0.098 | 0.13 |