MTL Barries - MTL5544 - MTL5544/S REPEATER POWER SUPPLY - 2-channel, 4/20mA, HART®, 2- or 3- wire transmitters

The MTL5544 is a two-channel repeater power supply that provides a fully-floating DC power source for a hazardous area transmitter and repeats the signal to a safe area. It isolates the hazardous and safe areas, allowing the power supply to energize a conventional two or three-wire transmitter while simultaneously replicating the 4-20 mA signal to drive loads in a safe area. For smart transmitters (like HART), it also allows bidirectional digital communication signals to be superimposed on the 4-20 mA loop.

Difference between MTL5544 and MTL5544S

The main difference is that the MTL5544 is a standard repeater power supply that sources current to drive loads in a safe area, while the MTL5544S is a "current sink" version that acts as a load for a current source located in the safe area. This means the MTL5544 powers two safe-area loads, while the MTL5544S receives a current from a safe-area power source and acts as a sink.

MTL5544

Function: Sources current into two safe-area loads.
Application: Use when you need to drive current to separate loads on the safe-area side.

MTL5544S

• Function: Acts as a current sink, accepting current from a separately powered current source in the safe area.
• Application: Use when you need to drive a load from a power source already present in the safe area.

Other Differences

• Hazardous-area wiring: Both models use a common base and blue connectors for the hazardous area field-wiring.
• Safe-area wiring: The MTL5544 uses the base connector for the safe-area connections, while the MTL5544S uses the removable grey connectors on the top and side of the module

Working principle

1. Hazardous Area (Input): The MTL5544 provides a fully-floating DC supply to a two or three-wire transmitter located in a hazardous area.
2. Signal Transmission: The transmitter responds by generating a 4-20 mA current signal proportional to the process variable.
3. Isolation: This signal is fed into the MTL5544, which provides electrical isolation between the hazardous and safe areas. This isolation prevents any fault currents from the safe area from reaching the hazardous area.
4. Safe Area (Output): The MTL5544 repeats the 4-20 mA current in a separate circuit, which can be used to drive a load in a safe area, such as a recorder or a PLC input.
5. HART communication: For smart transmitters, the unit passes the bidirectional digital communication signals superimposed on the 4-20 mA loop, allowing the transmitter to be interrogated from the safe area

The MTL5544 is a dual-channel, galvanically isolated repeater power supply (safety barrier) used in industrial process control systems. Its primary working principle involves providing power to devices located in a hazardous area while safely isolating the signals from the non-hazardous (safe) control area.

Key Working Principles

The main functions of the MTL5544 are:

• Intrinsic Safety (IS) Isolation: The unit uses advanced circuitry and isolating transformers to provide galvanic isolation between the hazardous and safe areas. This ensures that no fault in the safe area can pass excessive energy (voltage or current) into the hazardous area, thus preventing ignition of flammable atmospheres.
• Power Supply: It provides a fully-floating DC power supply to energize two independent 2-wire or 3-wire 4/20mA transmitters (sensors) situated within the hazardous area.
• Signal Repeater: It measures the current signal (4-20mA) from the hazardous area transmitters and precisely repeats that current value in separate circuits to drive two safe-area loads, such as a PLC (Programmable Logic Controller) or DCS (Distributed Control System) input card.
• HART Communication Pass-Through: For "smart" transmitters that use the HART communication protocol, the MTL5544 allows bi-directional transmission of digital communication signals superimposed on the 4/20mA analog signal. This allows operators or hand-held communicators in the safe area to interrogate the hazardous area device without interrupting the main signal loop.

Summary of Operation

• Input Power: The MTL5544 is powered by a 20 to 35V DC supply in the safe area.
• Hazardous Area Loop: It sends intrinsically safe power into the hazardous area to power the 2- or 3-wire field transmitters.
• Signal Transfer: The transmitter modulates the current loop (4-20mA) corresponding to the measured process variable (e.g., temperature, pressure).
• Isolation and Repeat: The unit receives this signal, isolates it electronically, and generates an identical, isolated current signal on the safe-area side to be read by the control system.

The MTL5544 provides a simple, DIN-rail mountable solution that simplifies installation by eliminating the need for high-integrity earthing often associated with traditional zener barriers.
For detailed technical specifications and safety approvals, you can refer to the official Eaton MTL datasheet.

 Full Datasheet