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Calibration · Glossary

What is an Accuracy Specification?

how makers state errorCalibration

An accuracy specification states how an instrument maker defines its maximum error, such as % of span, % of reading, % of URL or a combination.

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Accuracy Specification Explained

Flow meters often state % of rate above a cut point and a fixed value below it. Transmitters state reference accuracy in % of span, with extra terms in % of URL that grow at high turndown.

Convert every spec to the same units at your operating point before comparing instruments.

Accuracy Specification Formula

e = ± (a % of reading + b % of span)
a, bstated coefficients
emaximum error
Example: ± (0.1 % of reading + 0.05 % of span) on 0 to 100 at 40: ± (0.04 + 0.05) = ± 0.09.
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Calculators for Accuracy Specification

CalculatorAccuracy Specification CalculatorFree online calculator with formula and worked example.CalculatorTransmitter Turndown CalculatorFree online calculator with formula and worked example.

Free Downloads

Free downloadTransmitter Accuracy Calculation ExcelFree download in Excel and PDF.

Frequently Asked Questions

What is an Accuracy Specification?

An accuracy specification states how an instrument maker defines its maximum error, such as % of span, % of reading, % of URL or a combination.

What is reference accuracy?

Accuracy at reference conditions, usually including linearity, hysteresis and repeatability but not temperature effects.

Why does turndown worsen accuracy?

Terms stated in % of URL become a larger share of a small span.

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Related Terms

Calibration termAccuracyAccuracy is how close a measurement is to the true value; in specifications it is the maximum expected error.Calibration termTotal Probable ErrorTotal probable error combines independent error sources, such as reference accuracy, temperature and…Pressure termTransmitter TurndownTransmitter turndown is how far a transmitter span is reduced from its sensor upper range limit.

More Calibration Terms

Calibration termPrecisionPrecision is how closely repeated measurements of the same quantity agree with each other, regardless of…Calibration termRepeatabilityRepeatability is the closeness of successive readings of the same input under the same conditions, same…Calibration termReproducibilityReproducibility is the closeness of results for the same quantity when conditions change, such as…Calibration termHysteresisHysteresis is the difference between readings at the same input when approached from below (upscale) and…Calibration termLinearityLinearity is how closely an instrument output follows a straight line between input and output; non…Calibration termZero and Span ErrorZero and span error describe an instrument whose reading is offset at the bottom of the range (zero) or…

All calibration terms · Full glossary A to Z

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