Measurement Uncertainty: length_micrometer
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 |
|---|---|---|---|---|---|---|---|---|---|---|---|
| length_micrometer | calibration_certificate | 95 | 2 | normal | 2 | 0.004 | mm | Calibration expanded uncertainty k=2 for micrometer at NIST-traceable lab; typical 0.002-0.005 mm (2-5 um) for 0-25 mm range | mm | 0.002 | Type_B |
| length_micrometer | combined_standard_uncertainty | 95 | 2 | normal | 1 | 0.008 | mm | RSS of components: sqrt(0.003^2+0.002^2+0.002^2+0.001^2) approx 0.004 mm; U95 = 0.008 mm; 10x better than caliper | mm | 0.004 | Combined |
| length_micrometer | instrument_resolution | 95 | 2 | rectangular | 1.732 | 0.006 | mm | Outside micrometer resolution 0.001 mm (1 um); half-interval 0.0005 mm; u_res = 0.0005/sqrt(3) = 0.00029 mm; reported here as 0.003 mm including scale error and anvil flatness | mm | 0.003 | Type_B |
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