Measurement Uncertainty: flow_orifice_plate
GUM-compliant measurement uncertainty budget components and coverage factors for common engineering measurements. Covers Type A (statistical) and Type B (non-statistical) uncertainty sources with standard uncertainties, expanded uncertainties at k=2 (95%), and confidence levels for: length/dimension (caliper, micrometer, CMM, gauge block), mass (analytical balance, platform scale), temperature (Type K thermocouple, Pt100 RTD, IR pyrometer), pressure (Bourdon gauge, electronic transducer, liquid manometer), flow (orifice plate, turbine meter, Coriolis, ultrasonic transit-time), electrical (DMM, power analyzer), force (load cell), and torque (torque wrench). Also includes coverage factor reference rows (k=1/2/3, 68/95/99.7%) and distribution divisors (rectangular, triangular, normal, U-shaped). Per ISO/IEC Guide 98-3:2008 (GUM), NIST TN 1297, ISO/IEC 17025:2017.
| measurement type | uncertainty source | confidence level pct (%) | coverage factor k | distribution | divisor | expanded uncertainty k2 | expanded uncertainty unit | notes | standard uncertainty unit | standard uncertainty value | uncertainty type |
|---|---|---|---|---|---|---|---|---|---|---|---|
| flow_orifice_plate | bore_diameter_measurement | 95 | 2 | normal | 2 | 0.1 | pct_flow | Bore diameter d measurement uncertainty; 0.02 mm uncertainty in 100 mm bore -> 0.04% on d -> 0.08% on d^2 -> proportional flow error | pct_flow | 0.05 | Type_B |
| flow_orifice_plate | combined_standard_uncertainty | 95 | 2 | normal | 1 | 1.12 | pct_flow | Propagated via ISO 5167 sensitivity coefficients; u_Q/Q = sqrt((2*u_dP/dP/2)^2 + u_Cd^2 + ...) approx 0.56% flow; U95 = 1.1% flow | pct_flow | 0.56 | Combined |
| flow_orifice_plate | differential_pressure | 95 | 2 | normal | 2 | 0.5 | pct_DP | dP transmitter uncertainty: typical 0.1-0.25% FS (see pressure_transducer); differential pressure dominates flow uncertainty squared | pct_DP | 0.25 | Type_B |
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