Fan Performance Uncertainty Estimation
G.1 General Statement
Measurement uncertainty associated with the reported results was evaluated and estimated in accordance with JCGM 100:2008 (Guide to the Expression of Uncertainty in Measurement — GUM) and ISO/IEC 17025:2017, Clauses 7.6 and 7.2.
The uncertainty budget accounts for all significant identified contributors arising from the measurement process, instrumentation, test conditions, and operator interaction.
The reported expanded uncertainty U is obtained by multiplying the combined standard uncertainty uc by a coverage factor k = 2, corresponding to a confidence level of approximately 95 %, assuming a normal probability distribution.
Unless otherwise stated, the reported uncertainty applies only to the specific measurements performed and does not include long-term drift, aging effects, or future environmental changes.
G.2 Expanded Measurement Uncertainty by Measurement Type
| Measurement |
Expanded Uncertainty U (k=2, norm) |
| Fan Air Flow |
±1.9296 % of reading (k=2) — e.g. ±3.77 CFM at 25 CFM, ±5.00 at 89 CFM, ±10.31 at 250 CFM |
| Fan Static Pressure |
±2.422 Pa |
Air flow uncertainty is relative to the reading: U(Q) = 2·√[(1.8200)² + (0.019296·Q)²] CFM, valid over the declared measuring range 2.4 – 250 CFM.
The reported static pressure uncertainty applies over the 0 – 20 mmAq (0 – 196.1 Pa) measuring range of the Long Win LW-9266 apparatus. The apparatus can be extended to 100 mmAq (981 Pa) with the high static pressure throttle device; the uncertainty of that extended range has not been separately verified and the value stated above does not apply to it.
