Primary Element & Configuration
Identify the meter, select compliance framework, and configure the primary element type. This determines the discharge coefficient model, ISO 5167 formula uncertainty, and compliance pass/fail thresholds.
📋
AUDIT IDENTIFICATION
Appears on report🔧
INSTRUMENT & DOCUMENT REGISTER
EXPAND
Traceability: Record instrument identifiers, calibration certificate numbers, and maintenance references. These appear in the report appendix for audit traceability — they do not affect the calculation.
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COMPLIANCE FRAMEWORK
Select the regulatory or contractual framework to determine the pass/fail uncertainty threshold applied to the final result. You can also set a custom limit.
EU ETS MRR — Tier 1
Reg. (EU) 2018/2066, Annex II
U ≤ ±7.5%
EU ETS MRR — Tier 2
Reg. (EU) 2018/2066, Annex II
U ≤ ±5.0%
EU ETS MRR — Tier 3
Reg. (EU) 2018/2066, Annex II
U ≤ ±2.5%
EU ETS MRR — Tier 4
Reg. (EU) 2018/2066, Annex II
U ≤ ±1.5%
Fiscal / Custody Transfer
OIML R117 Class 0.5 / NFOGM
U ≤ ±1.0%
OIML R117 — Class 1.0
OIML R117-1:2007
U ≤ ±1.0%
OIML R117 — Class 1.5
OIML R117-1:2007
U ≤ ±1.5%
UK SMPMS / NSTA
UK Petroleum Measurement
U ≤ ±1.0%
Process Metering
General industrial
U ≤ ±2.0%
Custom Threshold
Contractual / site-specific
User-defined
Selected framework
EU ETS MRR — Tier 1
Uncertainty limit
≤ ±7.5%
⚠ Input validation issues:
Standards basis: Uncertainty evaluated per ISO 5168:2005 (flowmeter-specific standard referenced by ISO 5167-1:2022 Clause 8), implementing GUM (ISO/IEC Guide 98-3) with flow-specific sensitivity coefficients. Type A (statistical) and Type B (non-statistical) components evaluated separately and combined by RSS. Welch-Satterthwaite effective degrees of freedom applied when Type A contributions are present — coverage factor k adjusted per GUM G.4.
Where to find: Meter type on primary element tag, calibration certificate, and as-built P&ID / IDS.
◎
PRIMARY ELEMENT
◉
ORIFICE PLATE
ISO 5167-2:2022
Most Common
⬭
VENTURI TUBE
ISO 5167-4:2022
Low ΔP Loss
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FLOW NOZZLE
ISO 5167-3:2022
High Velocity
Tapping holes at pipe face. Standard ISO 5167-2.
Meter Geometry
Enter pipe bore D and primary element bore d with expanded (k=2) measurement uncertainties.
ISO 5168 sensitivity (Annex A): c(d) = 2 + 4β⁴/(1−β⁴) and c(D) = 4β⁴/(1−β⁴). At β=0.6, a 0.1% error in bore diameter contributes 0.23% to flow uncertainty.
Where to find: Bore d — calibration certificate (measured at 20°C reference). Bore D — dimensional inspection report of actual installed pipe internal diameter.
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DIMENSIONAL INPUTS
DN 25
DN 50
DN 80
DN 100
DN 150
DN 200
DN 250
DN 300
Measured internal bore at operating temperature
From dimensional inspection / calibration certificate
Precision bore ≈ ±0.013 mm typical
β (d/D)
—
β⁴
—
Sensitivity c(d)
—
Sensitivity c(D)
—
ISO 5167 validity
—
Process Conditions
Enter operating conditions and fluid properties. For gas, select how to specify line density. All density values must be at actual line conditions (operating P and T).
Line conditions vs reference: ISO 5167 computes actual volumetric flow at line P and T. Nm³/h and Sm³/h conversions are applied automatically for gas using the fluid's own density at reference conditions — not a hardcoded air density. ΔP uncertainty dominates with sensitivity coefficient 0.5.
Where to find: ΔP from transmitter datasheet; P and T from adjacent PT/TT instruments; density from fluid analysis, NIST WebBook, REFPROP, or process simulation.
Δ
DIFFERENTIAL PRESSURE TRANSMITTER
Maximum DP the capsule can measure — from transmitter nameplate / datasheet. Denominator for "% URL" accuracy specs.
mbar
Configured URV − LRV. Equal to URL if not ranged down; can be less. Denominator for "% span" specs.
mbar
Operating at —% of span, —% of URL
URL vs Span vs Reading:
% URL — absolute error = value% × URL. Error is fixed regardless of span or operating point. Used by most smart transmitters (Rosemount 3051, EJX, ABB 266) for reference accuracy.
% Span — absolute error = value% × calibrated span. Equals % URL when span = URL. Larger than % URL when ranged down (span < URL).
% Reading — absolute error = value% × actual ΔP. No turndown amplification. Used for some high-accuracy digital transmitters.
| Error Term | Value (%) | Basis | → % of Reading | Notes / Source |
|---|---|---|---|---|
| Reference accuracy | — | Datasheet; smart tx ≈ 0.04–0.075% URL | ||
| Long-term stability | — | Per year since last calibration | ||
| Impulse line / seal error | — | Head correction; 0 if remote-seal | ||
| Calibration uncertainty (k=2) | — | From calibration certificate |
Environmental & Installation Effects (enable to include in budget)
LINE PRESSURE EFFECT
e.g. 0.1% URL per 1000 psi — static pressure on DP cell zero/span shift
AMBIENT TEMPERATURE EFFECT
e.g. 0.1% URL per 28°C — zero/span shift due to ambient T change from calibration
OTHER EFFECTS
vibration, power supply variation, RFI/EMI, mounting position
PT
LINE PRESSURE & TEMPERATURE
For gas: enters density uncertainty via EOS
RTD Cl.B ≈ ±0.3 K; Cl.A ≈ ±0.15 K; TC type K ≈ ±2 K
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FLOW COMPUTER COMPENSATION
Does the flow computer / DCS apply real-time compensation? Many installations correct the raw ΔP-derived flow for changes in operating P, T, or ρ. This significantly affects how uncertainties propagate. If compensation is present, P and T transmitter uncertainties feed into the compensated output and are already partially accounted for. If no compensation is applied, the uncertainty in assumed (design-basis) P, T, or ρ values becomes a fixed bias error.
Where to find: Flow computer configuration sheets, DCS/PLC logic diagrams, P&ID showing PT / TT / DT connections to flow computer, instrument index / IDS.
ρ
LIQUID FLUID PROPERTIES — LINE CONDITIONS
At operating P and T — from process lab, NIST WebBook, or simulation
Design-basis Type B — field lab samples refined in Step 4
Water @ 20°C ≈ 0.001002 Pa·s
K
LIQUID COMPRESSIBILITY (BULK MODULUS)
INCLUDE
Liquid compressibility: Liquids compress slightly under pressure. Density correction: ρ_P = ρ_ref × (1 + ΔP/K) where K = bulk modulus and ΔP = gauge pressure at line conditions. This becomes significant at high line pressures (>10 bara) or for compressible liquids (crude oil, methanol). If your design-basis density was measured at a different pressure, enable this to quantify the residual uncertainty if not corrected.
Field Measurements & Operational Data
Optional Type A uncertainties from repeated measurements per ISO 5168 Clause 5.2. Combined with Type B instrument-spec values by RSS. Leave disabled if no field data available.
Type A evaluation (ISO 5168 Clause 5.2): u_A = s / √n. For density: u(ρ) = √[u_B² + u_A²]. For ΔP: shown as a separate line alongside Type B spec. Industry best practice for fiscal metering audits (NFOGM Handbook, UK SMPMS, API MPMS Ch.22).
Where: Density — monthly/weekly lab sample reports (LIMS). ΔP/flow — DCS/SCADA historian exports at verified steady-state periods.
ρ
FLUID DENSITY — LAB SAMPLE DATA (TYPE A)
ENABLE
Δ
ΔP / FLOW — OPERATIONAL DATA (TYPE A)
ENABLE
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ANNUAL FLOW PROFILE — UNCERTAINTY BACK-TEST
ENABLE
Instrument & Installation Errors
Additional systematic error sources combined with Type B instrument-spec values from Step 3 and Type A from Step 4 by RSS per ISO 5168 Clause 7.
ISO 5168:2005: Directly referenced by ISO 5167-1:2022. For a permanently installed meter, all errors are treated as systematic (rectangular or normal distributions) — conservative and standard practice for fiscal metering.
Cd
DISCHARGE COEFFICIENT
INCLUDED
e.g. edge wear since last inspection; 0 if recently verified
INCLUDED
Residual after ISO 5167 straight-run requirements met; 0 if flow conditioner validated
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SIGNAL PROCESSING & DATA ACQUISITION
INCLUDED
INCLUDED
INCLUDED
INCLUDED
D correction for T vs 20°C reference; 0 if not applied
k
REPORTING
MeterProof — DP Flowmeter Uncertainty Analysis Report
Uncertainty Analysis Report
Expanded uncertainty per ISO 5168:2005, with sensitivity coefficients from ISO 5167 and Type A/B separation per GUM (ISO/IEC Guide 98-3). Welch-Satterthwaite effective degrees of freedom applied when Type A data is present.