Open Access
Table 1
Uncertainty budget at 0 °C for the two generators.
| Source | Symbol | Distribution | Divisor | Sensitivity coefficient | Value for (1-T) generator (°C) | Value for (2-T) generator (°C) | Method of estimation |
|---|---|---|---|---|---|---|---|
| Type A | |||||||
| Repeatability for 1st SPRT | 1st SPRT Rep. | Normal | 1 | 1 | 0.009 | 0.0013 | Standard deviation of measurements |
| Repeatability for 2nd SPRT | 2nd SPRT Rep. | Normal | 1 | 1 | – | 0.0002 | Standard deviation of measurements |
| Type B | |||||||
| 1st SPRT calibration | U(ts sprt cal) | Normal | 2 | 1 | 0.002 | 0.002 | Calibration certificate |
| SPRT drift | U(ts sprt drift) | Rectangular | √3 | 1 | 0 | 0 | Max. difference between two successive calibrations of the standard |
| 1st bath stability | U(ts stab) | Rectangular | √3 | 1 | 0.006 | 0.006 | Difference between maximum and minimum value of measurements |
| 2nd SPRT calibration | U(ts sprt cal) | Normal | 2 | 1 | – | 0.002 | Calibration certificate |
| 2nd bath stability | U(ts stab) | Rectangular | √3 | 1 | – | 0.006 | Difference between maximum and minimum value of measurements |
| SPRT resolution (indicator unit) | U(ts ind res) | Rectangular | 2√3 | 1 | 0.0001 | 0.0001 | Digital indicator = 0.5 of resolution |
| Bridge calibration | U(ts cal) | Normal | 2 | 1 | 0.0005 | 0.0005 | Calibration certificate |
| Saturator efficiency | U(ts sat eff) | Normal | 1 | 1 | −0.1413 | 0.0041 | The temperature difference between bath temperature that containing the saturator and the air temperature inside the saturator |
| Saturator homogeneity | U(ts sat hom) | Normal | 1 | 1 | – | 0.01 | The temperature difference between saturator inlet and exit |
| Saturator temperature stability | U(ts sat stab) | Rectangular | √3 | 1 | – | 0.0047 | Difference between maximum and minimum value of measurements |
| Test-chamber efficiency | U(ts cham eff) | Normal | 1 | 1 | – | 0.0057 | The temperature difference between bath temperature that containing the chamber and the air temperature inside the saturator |
| Test-chamber homogeneity | U(ts cham hom) | Normal | 1 | 1 | – | 0.01 | The temperature difference between chamber inlet and exit |
| Test-chamber temperature stability | U(ts cham stab) | Rectangular | √3 | 1 | – | 0.0005 | Difference between maximum and minimum value of measurements |
| Dew-point hygrometer | U(tm cal) | Normal | 2 | 1 | 0.06 | 0.06 | Calibration certificate |
| Resolution of hygrometer | U(tm hygro res) | Rectangular | 2√3 | 1 | 0.01 | 0.01 | Digital indicator = 0.5 of resolution |
| Drift of hygrometer | U(tm hygro dri) | Rectangular | √3 | 1 | 0.01 | 0.01 | Max. difference between two successive calibrations of the standard |
| Combined uncertainty | 0.073 | 0.033 | |||||
| Expanded uncertainty (k = 2) | ±0.145 | ±0.066 | |||||
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