NAMUR basic information

The abbreviation of NAMUR, “User Association of Automation Technology in Process Industries” identifies an international association for users of automation technology that considers the interests related to standardization, devices and measurement control (or similar) of the Process Industries as its major task. In this role, the NAMUR releases the so called NE (proposed standards), each numbered continuously.

Information with regard to the implementation of this recommendation in Beckhoff products are specified in sections “Technical data” and “Process data” of this documentation.

Analog measured values

The analog output value of a sensor that can be measured among other things as a certain current value represents the measurement information (M).

By means of NAMUR NE43 a recommendation – irrespective of the sensor manufacturer – for standardized failure information (A) is defined in addition to the measurement information (e.g. malfunction of a measurement converter, error in connective wires, failure of an auxiliary energy etc.). The failure information states that there is an error in the measuring system. This concerns the analog output signal of sensors in a current loop and therefore in the form of a current value. A current value lying outside of the limits defined by NE43 is defined invalid as measurement information and then interpreted as failure information. The following diagram illustrates this:

Digital measured values

The supply as well as the evaluation of the fed back current of the sensor via a 2‑wire connection is done by a by the DC switching amplifier. This evaluates the analog current signal using prescribed limit and hysteresis values in transition junctions in accordance with the IEC / DIN EN 60947-5-6 (formely NAMUR NA01) standard. The switching states will be passed through (if necessary, galvanic isolated) from the field side to the higher level control. Starting with a current loop, adherence to the limits defined by NAMUR is required in this case too for classification as valid measurement information. If these limits are exceeded there is generally an error, i.e. either a short circuit or an interruption of the 2‑wire connection incl. the sensor.