Glossary · Process instrumentation and analytical measurement
NAMUR signal
Also known as: NAMUR sensor interface, NAMUR proximity switch signal
German: NAMUR-Signal
In process instrumentation, a NAMUR signal is a two-wire DC interface for binary sensors in which the sensor changes its current consumption between defined low and high levels, typically below about 1.2 mA and above about 2.1 mA at a nominal 8.2 V supply, so that the switching amplifier can detect both switching states and line faults.
- Process instrumentation
- Standards
- Process industry
In one sentence
A NAMUR signal is a two-wire interface for binary sensors that switch between low and high current levels, allowing wire break and short detection.
Example
NAMUR proximity sensors on valve actuators report open and closed positions via an intrinsically safe switching amplifier that also detects a cut cable.
How it applies
- Engineering: NAMUR sensors need a switching amplifier or an input card with NAMUR evaluation; they cannot be connected directly to standard 24 V digital inputs. Their low energy makes them well suited to intrinsically safe circuits.
- Diagnostics: Currents far below the low level indicate a wire break; currents far above the high level indicate a short circuit. The amplifier can signal these as faults.
- Commissioning: Enable line fault detection where the application requires it, and check the switching direction of the amplifier output.
- Documentation: Name the interface as NAMUR per IEC 60947-5-6 in device lists and loop diagrams, and state whether line fault detection is active.
NAMUR signal vs. NAMUR NE 43
The NAMUR signal is a binary sensor interface. NAMUR NE 43 is a recommendation for failure levels of analog 4–20 mA transmitters.