2-Wire Sensors

2-wire sensors do not have separate connections for the load current circuit and the voltage supply. 2-wire NAMUR sensors must be operated at an isolated switch amplifier designed for this purpose. Magnetically actuated Reed switches are electromechanical switches and are operated in series to the connected load. Reed switches can be connected in series or in parallel without any restrictions.

Wire sensors according to NAMUR (NAMUR sensors) are named after the User Association of Automation Technology in Process Industries ("Normenarbeitsgemeinschaft für Mess- und Regeltechnik der chemischen Industrie"). These are 2-wire sensors according to EN 60947-5-6 (VDE 0660, part 212) that have a continuous or a noncontinuous distance/current characteristic.

Area 0: unactuated area
Red area between 0/I: impermissible area of the switch amplifier
Area I: actuated range
Area ≤ 0.15 mA: lead breakage
Area ≥ 6.5 mA: short circuit

In addition, Pepperl+Fuchs offers NAMUR sensors with binary switching characteristics. NAMUR sensors with this output characteristic are marked with "N0" (normally-closed characteristics) or "N1" (normally-open characteristics) in the type code.

Area 0: unactuated area
Red area between 0/I: impermissible area of the switch amplifier
Area I: actuated range
Area ≤ 0.15 mA: lead breakage
Area ≥ 6.5 mA: short circuit

Sensor Connection—Example

Pepperl+Fuchs offers various switch amplifiers for NAMUR sensors used in explosion-protection applications and standard applications.

Note: In explosion-protection applications, the operating location of the intrinsically safe NAMUR sensor is located in the explosion-hazardous area. The isolated switch amplifier must be installed outside the explosion-hazardous area.
A blue-sheathed sensor cable visually identifies the NAMUR circuit as intrinsically safe.

Example:

NAMUR Sensor Versions

NAMUR sensors are marked with the following in the third block of the Pepperl+Fuchs order designation:

–N = continuous distance/current characteristic or

–N0 = non-continuous distance/current characteristic

The sensors are available in the following switching element functions:

• Normally-closed (N/N0)
• Normally-open (1N/N1)
• Normally-closed 2-channel (N4)

NAMUR sensors are usually connected to external switch amplifiers that convert the current variation into a binary output signal.