TURCK MK33-LI-EX0 – Intrinsically Safe Isolating Switching Amplifier for NAMUR Sensors in Hazardous Areas

The TURCK MK33-LI-EX0 is an intrinsically safe isolating switching amplifier designed to interface NAMUR proximity sensors or dry contacts from Zone 0/1/2 into the safe area. From my experience, it’s a practical way to bring clean, galvanically isolated signals into PLCs or safety relays without overcomplicating the panel. You might notice that the MK33 line is built for reliability first—stable switching, clear diagnostics, and robust isolation typically suited for chemical plants, oil & gas skids, grain handling lines, and any area that needs Ex ia protection.

Order Placement Process and Guarantees

• – Warranty period: 365 days

• – Delivery time: 1 week for in-stock items; no more than one month at the latest

• – Payment terms: 50% advance payment, full payment before delivery

– Express delivery: FedEx, UPS, DHL

Key Features

• Intrinsically Safe Input (Ex ia) – Interfaces directly with NAMUR proximity sensors or dry contacts located in hazardous areas, typically Zone 0/1.
• Galvanic Isolation – Safe-area control equipment is electrically isolated from the field device, which in many cases helps reduce ground loops and noise.
• Reliable Switching Output – Provides a clean output signal (commonly relay) for PLCs, safety relays, or alarms; seems to be well-suited for on/off detection.
• Line Fault Detection – Open/short detection on the NAMUR loop typically speeds up troubleshooting in the field.
• DIN-rail, Slim Housing – Compact 22.5 mm style housing helps when cabinet space is tight.
• Status LEDs – Quick visual check for power, input status, and fault conditions—one thing I appreciate when commissioning.
• Robust Industrial Design – Built for continuous operation with wide ambient temperature capability common to process plants.

Technical Specifications

Related or Supporting Products

• TURCK IMX12-DOX – Ultra-slim 12.5 mm isolating switching amplifier; great when you need higher channel density.
• TURCK IMX12-EX-AI – Analog Ex isolator for 4–20 mA loops; pairs with transmitters rather than NAMUR switches.
• TURCK MK13 series – Similar interface modules with alternative supply and output options for legacy panels.
• TURCK NAMUR sensors (e.g., Bi2-…-N, Ni8-…-N) – Compatible field devices for the hazardous area side.

A maintenance lead recently told me the MK33’s simple LED fault indication helped them pinpoint a broken field cable within minutes—small detail, big time saver during a shutdown.

Installation & Maintenance

• Panel & Environment – Mount on a 35 mm DIN rail inside a ventilated enclosure to IP54 or better. Keep away from heat sources; allow space for airflow on the sides.
• Wiring – Follow Ex wiring practices: segregate hazardous-area leads from safe-area wiring. Use shielded cable for the NAMUR input when runs are long. Ground per the certificate and plant standards.
• Power – Provide a clean 24 VDC supply within the specified 20…30 VDC range in most cases. Protect the supply with an appropriately rated circuit breaker or fuse.
• Commissioning – Verify correct polarity on NAMUR inputs; check LEDs for status and line fault. Confirm output logic (NO/NC) matches PLC expectations.
• Routine Maintenance – Quarterly visual check of terminals for loosening; light dust cleaning. No user calibration typically required; keep firmware/technical bulletins in view if the unit supports updateable electronics.
• Safety – Only qualified personnel should connect the Ex side. Always comply with the device control drawing and the specific ATEX/IECEx certificate conditions.

Quality & Certifications

• CE compliant; RoHS conform
• ATEX and IECEx approvals for Ex ia input circuits (model-dependent, install per certificate)
• UL/cUL recognition for industrial control equipment in many cases
• Manufacturer warranty: 365 days