Phoenix ContactPI-EX-NAM/RNO-NESingle-Channel NAMUR Isolating Amplifier, Ex ia Intrinsically Safe Input, Relay N/O Output, Line Fault Detection, SIL 2

Product Description

What this part is:
A Phoenix Contact PI-EX-NAM/RNO-NE intrinsically safe signal isolator, order number 2835341. It is a single-channel Ex i binary input module: a NAMUR proximity sensor or mechanical switch mounted in a hazardous area connects to the intrinsically safe input, and the resulting binary state is repeated as a relay contact in the safe area. The module provides galvanic three-way isolation between input, output and supply.

Hazardous-area certification:
This module carries the intrinsically safe field circuit approval that is the whole reason for its existence. The input circuit is certified Ex ia, marked ATEX II (1) GD [Ex ia] IIC, which means the input may be routed into Zone 0 while the module itself sits in the safe area or in Zone 2. The module body is separately rated II 3 G Ex nAC IIC T4 X for Zone 2 installation. Energy limiting in the input circuit is what allows field wiring into a flammable atmosphere without an explosion-proof enclosure.

The module is also assessed to SIL 2 in accordance with EN 61508, so it can form part of a safety instrumented function up to that integrity level, and it complies with NAMUR recommendation NE 21 for electromagnetic compatibility of process control equipment.

What these specs mean in practice:
A NAMUR sensor signals its state by changing current draw rather than by switching a contact, which is what makes line monitoring possible. Because the sensor always draws some current, the amplifier can distinguish four conditions instead of two: sensor active, sensor inactive, lead breakage, and short circuit. A broken cable therefore reports as a diagnosed fault rather than silently reading as an inactive sensor, which is the failure mode that matters on a valve position or level switch.

Galvanic three-way isolation separates the field circuit, the relay output and the supply from one another, so earth potential differences between the field and the control cabinet do not couple into the signal, and a fault on one side stays on that side.

Published specifications:

Function: NAMUR isolating amplifier, Ex i binary input
Channels: 1
Input: NAMUR proximity sensor or mechanical switch, intrinsically safe circuit
Input circuit voltage: 10.6 V maximum
Input circuit current: 33 mA maximum
Output: relay, N/O contact
Line fault detection: lead breakage and short circuit
Isolation: galvanic three-way, input to output to supply
Supply voltage: 24 V DC
Ex marking, input circuit: ATEX II (1) GD [Ex ia] IIC
Ex marking, module: II 3 G Ex nAC IIC T4 X
Functional safety: SIL 2 per EN 61508
EMC: NAMUR NE 21
Order number: 2835341

Quantity and configuration:
Sold as 1 Pc — one isolating amplifier module. The PI-EX-ES-1/3 basic terminal block (order number 2835325) is a separate accessory and is not included, as is the TT-PI-EX-TB surge protection device (order number 2858386).

Installation and setup notes:
Modules in the PI-EX range plug into a basic terminal block that carries the field and supply wiring, so an existing installation with that terminal block in place accepts the module directly. The intrinsically safe input wiring is kept separate from non-intrinsically-safe wiring and is conventionally identified in light blue. No configuration switches are required for NAMUR input operation.

Interchange guidance:
The PI-EX-NAM/RNO (order number 2835053) is the same NAMUR-input, relay-output function without the NE suffix variant features, so it is a related device in the same family rather than an identical article. Within Phoenix Contact’s wider range the MACX MCR-EX-SL-NAM-R (order number 2865434) performs the equivalent NAMUR isolating switch amplifier duty in the MACX form factor, with a different footprint and terminal arrangement. A direct replacement matches order number 2835341.