MTL MTL5549 – Intrinsically Safe 4–20 mA Isolator for Hazardous-Area Transmitters

The MTL5549 sits in the proven MTL5500 series and is typically used as a repeater power supply for 2‑wire transmitters in hazardous areas. From my experience, it’s the kind of “fit-and-forget” analog isolator you drop into a marshaling cabinet when you need clean 4–20 mA with galvanic isolation and HART pass-through, without eating up panel space. You might notice that it’s slim, DIN-rail friendly, and plays nicely with existing DCS/PLC analog input cards—exactly what most brownfield upgrades need.

Order Placement Process & Guarantees

• – Warranty: 365 days from shipment

• – Delivery: 1 week if in stock; no more than 1 month latest

• – Payment: 50% advance payment; full payment prior to delivery

– Express options: FedEx, UPS, DHL

Key Features

• Repeater power supply for 2‑wire transmitters – Powers a hazardous‑area transmitter and reproduces a clean 4–20 mA signal on the safe side.
• Galvanic isolation – Breaks ground loops and improves noise immunity between field and control system, which in many cases stabilizes readings.
• HART transparency – Typically supports HART pass‑through so you can configure and diagnose devices without extra wiring.
• Slim DIN‑rail footprint – Compact module width helps increase cabinet density; easy to slot alongside other MTL5500 units.
• Safe- and hazardous‑area segregation – Clear terminals and labeling reduce wiring mistakes during hot-cutover work.
• System-friendly power – Runs from a standard 24 VDC cabinet supply, either via the backplane or terminals.

Typical Use Cases

• Loop-isolated AI channels for pressure, flow, or level transmitters located in Zone 1/Division 1 areas.
• Brownfield upgrades where you need HART diagnostics without changing existing AI cards.
• Long cable runs where ground potential differences and noise seem to be causing drift or spikes.

Technical Specifications

Related or Supporting Products

• MTL5546 – Repeater power supply with similar function; in many cases chosen where channel density or specific drive levels are required.
• MTL5541 – Solenoid/alarm driver; use this when you need to drive coils or audible/visual alarms rather than power a transmitter loop.
• MTL5511 / MTL5513 – Switch/NAMUR proximity detector interfaces for discrete inputs from hazardous areas.
• MTL4549 – 4500‑series counterpart for sites standardized on the MTL4500 footprint.
• MTL4850 HART Multiplexer – Pulls HART diagnostics from multiple loops without disturbing the analog measurement.

Installation & Maintenance

One thing I appreciate is how straightforward these are to commission. Still, a few habits save time and rework:

• Cabinet & mounting – Install on a grounded DIN rail inside a ventilated cabinet. Keep IS field wiring segregated from non‑IS wiring with clear trunking separation.
• Power & earthing – Use a clean 24 VDC source. Bond the backplane/rail earth as recommended to maintain isolation integrity.
• Wiring – Hazardous‑area connections to the field transmitter; safe‑area output to the DCS/PLC AI card. Maintain polarity and loop continuity; leave room for HART test clips if you routinely connect handhelds.
• Environmental – Operate within the stated temperature range; avoid high‑vibration spots or heat sources that can accelerate drift.
• Routine checks – Verify 4–20 mA span during instrument calibrations, clean terminal areas to prevent ingress, and document any device label revisions. Firmware updates aren’t typically applicable for this type of analog isolator.
• Safety – Confirm hazardous‑area classification and entity parameters match your transmitter. Never hot‑swap in a live hazardous environment.

Quality & Certifications

• Manufacturer compliance typically includes CE and RoHS for industrial control equipment.
• Intrinsic safety approvals (e.g., ATEX/IECEx/FM/CSA) are associated with the MTL5500 series; please verify exact markings on your MTL5549 unit and local approvals required by your site.
• Warranty: 12 months from shipment as stated above.

Field note from a recent turnaround: swapping older barriers for MTL5549 units tightened up loop stability on a few noisy transmitters, and HART diagnostics came through reliably without adding any external modems. That’s usually the kind of low‑risk upgrade operations teams like—clean, quick, and traceable.