Namur

The acronym NAMUR identifies a family of proximity sensors having a completely different type of output from that of the common NPN and PNP sensors. NAMUR is a type of sensor output that gives an on or off indication.

The abbreviation NAMUR draws its origins from the German language and literally means “normenarbeitsgemeinschaft für Mess- und Regeltechnik in der Chemischen Industrie”, in other words “association for the standardization of measurement and control in the chemical industries”.
The connection has two wires only since these sensors have current and not voltage outputs. The power supply necessary for the functioning of the electronics inside the sensor is also conveyed through these two wires.

A NAMUR sensor is a non-amplified sensor that supplies two different signal levels depending upon switch state. These signal levels are low-level current. A logic interface circuit, controller, PLC, DCS, or intrinsically safe (IS) barrier is needed to read these current levels. The standards for NAMUR output sensors are EN 60947-5-6:2000 and IEC 60947-5-6:1999.

NAMUR sensors are typically used in potentially explosive environments, as intrinsically safe devices: the energy that passes through them does not constitute an ignition hazard. If it is also necessary to have a certain degree of functional safety, if the sensor provides protection in this sense, safety hardware with NAMUR inputs is also available.