Glossary · Process instrumentation and analytical measurement
NAMUR NE 43
Also known as: NE 43, NE43 failure signal
German: NAMUR NE 43
In process instrumentation, NAMUR NE 43 is a NAMUR recommendation that standardizes the signal levels of 4–20 mA transmitters for failure information, separating the range for measurement information (3.8 to 20.5 mA) from failure signals (at or below 3.6 mA, or at or above 21 mA).
- Process instrumentation
- Standards
- Process industry
In one sentence
NAMUR NE 43 standardizes 4–20 mA signal levels so control systems can tell measured values from transmitter failure signals.
Example
A temperature transmitter configured to NE 43 drives its output to 21.5 mA on a sensor break, and the control system raises a failure alarm instead of showing a high temperature.
How it applies
- Engineering: Transmitters are configured for downscale (low) or upscale (high) failure signaling. The choice should follow the fault analysis: which direction leads the control logic to a safe reaction.
- Control system: Analog inputs must evaluate the same thresholds. Values slightly outside 4–20 mA but within the NE 43 measurement range are still measurements; values beyond the failure thresholds are faults.
- Commissioning: Test the failure reaction, for example by simulating a sensor break, and check that the alarm and the process reaction are as specified.
- Documentation: State the configured failure direction for each transmitter in the instrument list and describe the alarm and the operator response in the operating manual.
NE 43 vs. NAMUR signal
NE 43 concerns analog 4–20 mA transmitter signals. The NAMUR signal is a different interface for binary sensors defined in IEC 60947-5-6. Both carry the NAMUR name, which often causes confusion.