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Signals and PLC · Glossary

What is NAMUR NE43?

fault current levelsSignals and PLC

NAMUR NE43 is a recommendation that defines 4 to 20 mA signal levels for measurement and for transmitter failure.

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NAMUR NE43 Explained

Valid measurement runs from 3.8 to 20.5 mA. Values at or below 3.6 mA or at or above 21.0 mA indicate a failure.

The transmitter burnout direction (upscale or downscale) is chosen so a failure drives the loop to the safe side.

NAMUR NE43: Typical Values

Measurement range3.8 to 20.5 mA
Failure, low≤ 3.6 mA
Failure, high≥ 21.0 mA
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Calculators for NAMUR NE43

CalculatorNAMUR NE43 CheckerFree online calculator with formula and worked example.CalculatorAnalog Scaling CalculatorFree online calculator with formula and worked example.

Free Downloads

Free download4 to 20 mA Cheat SheetFree printable PDF cheat sheet.Free downloadHART Transmitter Configuration Record TemplateFree download in Excel and PDF.

Frequently Asked Questions

What is NAMUR NE43?

NAMUR NE43 is a recommendation that defines 4 to 20 mA signal levels for measurement and for transmitter failure.

Upscale or downscale burnout?

Choose the direction that causes a safe action: for a high level trip, upscale; for a low flow trip, downscale.

Must the DCS be set too?

Yes, the input card or software must alarm on the NE43 fault levels.

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4 to 20 mA current loop explained

A practical guide on instrumentationblog.in with more detail on NAMUR NE43 and how it is applied on real plants.

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Related Terms

Signal termLive ZeroLive zero means the lowest signal value (4 mA) is above zero, so a broken loop (0 mA) can be told apart…Safety termDiagnostic CoverageDiagnostic coverage is the fraction of dangerous failures that automatic diagnostics detect.Signal term4 to 20 mA Current LoopA 4 to 20 mA current loop sends a measurement as a current between 4 and 20 mA, which is not affected by…

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