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Measurement Uncertainty Calculator

AGA Error Budget & RSS Uncertainty Propagation

AGA / ISO Measurement Uncertainty Analysis
Calculates total measurement uncertainty using root-sum-square (RSS) propagation for orifice (AGA 3), turbine (AGA 7), ultrasonic (AGA 9), and Coriolis (AGA 11) meter systems. Includes pulsation error, turndown effects, and energy uncertainty.

Meter System

Transmitter Uncertainties

% rdg
Typical: 0.04-0.10% for smart transmitters
% rdg
Typical: 0.04-0.10% for pressure transmitters
°F
RTD + transmitter combined error
%
Actual DP as % of transmitter full scale (100% = no turndown)

Additional Factors

% HV
GC or online chromatograph heating value uncertainty
%
RMS DP pulsation / mean DP (0% = no pulsation). Orifice only.
%
Piping configuration, swirl, upstream disturbances
%
A/D conversion + calculation truncation

Orifice Parameters

%
Discharge coefficient: 0.5% typical for AGA 3 compliant installations
-
AGA 3 valid range: 0.10 to 0.75
in
Tolerance typically ±0.0005" for custody transfer plates

RSS Uncertainty Propagation

U_total = √(Σ(Si × ui)²)
Si = Sensitivity coefficient (partial derivative)
ui = Individual uncertainty source (%)
RSS = Root-Sum-Square combination
95% = Coverage factor k=2

Standards & References

  • AGA Report No. 3
    Orifice Metering (ISO 5167)
  • AGA Report No. 7
    Turbine Metering
  • AGA Report No. 9
    Ultrasonic Metering
  • AGA Report No. 11
    Coriolis Metering
  • ISO/IEC Guide 98-3 (GUM)
    Guide to Expression of Uncertainty

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