Measurement Uncertainty: electrical_multimeter_dmm
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 |
|---|---|---|---|---|---|---|---|---|---|---|---|
| electrical_multimeter_dmm | calibration | 95 | 2 | normal | 2 | 0.1 | pct_rdg | 6.5-digit DMM calibration: 90-day spec for DC voltage 0.0015% rdg + 0.0002% FS; for practical 3.5-5 digit field DMM U95 = 0.1% reading | pct_rdg | 0.05 | Type_B |
| electrical_multimeter_dmm | combined_standard_uncertainty | 95 | 2 | normal | 1 | 0.12 | pct_rdg | RSS: sqrt(0.05^2+0.03^2+0.01^2) = 0.059% rdg; U95 = 0.12% of reading for typical field DMM voltage measurement | pct_rdg | 0.06 | Combined |
| electrical_multimeter_dmm | resolution | 95 | 2 | rectangular | 1.732 | 0.06 | pct_FS | DMM resolution: 3.5 digit -> 1 count in 2000; half digit = 0.025% FS; u = 0.025/sqrt(3) = 0.014% FS; combined with zero drift 0.03% FS | pct_FS | 0.03 | Type_B |
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