MTL Instruments MTL5500 Series Modules: MTL5573 Temperature Converter —

Technical Dossier

Product Details And Specifications

MTL Instruments MTL5500 Series: Comprehensive Module Range and Technical Overview

The MTL5500 series, manufactured by MTL Instruments (now part of Eaton's MTL product line), represents one of the most widely deployed families of intrinsically safe signal conditioning modules in global heavy industry. Installed across petrochemical complexes, offshore platforms, nuclear facilities, and refinery control rooms, the MTL5500 range provides certified IS (Intrinsically Safe) and Ex ia barriers and isolators that interface field instruments in hazardous Zone 0/1/2 areas with safe-area DCS, PLC, and SCADA systems. Its DIN-rail form factor, passive and active variants, and broad agency certifications (ATEX, IECEx, FM, CSA) have made it a de facto standard in brownfield and greenfield process automation projects worldwide.

The Evolution of MTL5500 Architecture

The MTL5500 series was introduced as a successor to the MTL4500 range, transitioning from bulkier, individually wired barriers to a compact, plug-in DIN-rail module architecture. Early variants (circa late 1990s) focused on passive Zener barriers for simple on/off and analog signal isolation. The architecture evolved through the 2000s to incorporate active isolators with galvanic separation, eliminating the need for intrinsically safe earth bonding and simplifying installation in large marshalling cabinets. The MTL5573 specifically addresses RTD and thermocouple temperature signal conditioning, converting millivolt and resistance inputs from Zone 1 field sensors into standardized 4–20 mA or voltage outputs for safe-area receivers. Compatibility with legacy MTL4500 wiring infrastructure was maintained through consistent terminal pitch and equivalent functional mapping, enabling phased migration without full cabinet redesigns. As the MTL5500 series has entered its mature/end-of-life phase, long-term maintenance support and spare parts availability have become the primary procurement concern for asset owners operating 15–25 year plant lifecycles.

MTL5500 Full Catalog & Functionalities (SKU List)

The following SKUs represent verified, commonly deployed modules within the MTL5500 series, classified by functional category:

Temperature Input / Signal Converters

• MTL5573: RTD/thermocouple to 4–20 mA temperature converter, single-channel, IS input
• MTL5575: Dual-channel RTD/thermocouple temperature converter with 4–20 mA outputs
• MTL5576-RTD: RTD input isolator/converter, 3-wire PT100, 4–20 mA output
• MTL5576-THC: Thermocouple input isolator, mV signal, 4–20 mA output, CJC included

Analog Input Isolators

• MTL5541: 4–20 mA isolator/repeater, single-channel, loop-powered, ATEX/IECEx certified
• MTL5544: 4–20 mA isolator with HART signal transparency, single-channel
• MTL5544A: 4–20 mA HART isolator, dual-channel, active output
• MTL5546: 4–20 mA isolator, single-channel, with line fault detection
• MTL5549: 4–20 mA isolator/repeater, dual-channel, galvanically isolated

Analog Output Isolators

• MTL5561: 4–20 mA output driver/isolator, single-channel, DCS to field
• MTL5563: 4–20 mA output isolator with HART pass-through, single-channel

Digital Input (DI) Modules

• MTL5511: Single-channel switch/proximity detector interface, IS input, relay output
• MTL5514: Dual-channel switch detector, IS input, transistor output
• MTL5521: Single-channel switch detector with line fault detection, relay output
• MTL5523: Dual-channel switch detector, IS input, solid-state output

Digital Output (DO) / Solenoid Drivers

• MTL5531: Single-channel solenoid/alarm driver, IS output, 24 VDC
• MTL5532: Dual-channel solenoid driver, IS output, line fault detection

Pulse / Frequency Input

• MTL5582: Pulse/frequency input isolator, IS input, frequency output to safe area

Sourcing Hard-to-Find & Obsolete MTL5500 Parts

MTL Instruments has progressively transitioned the MTL5500 series toward end-of-life status, with several SKUs discontinued and replaced by the MTL5000 LPHD and SolaHD MTL product lines. For plant operators running DCS platforms such as Honeywell TDC 3000, Yokogawa CENTUM, or ABB Advant that were originally commissioned with MTL5500 modules, sourcing direct replacements is operationally critical — cross-platform substitution requires re-engineering of IS loop calculations and cabinet layouts.

DriveKNMS maintains a dedicated inventory of MTL5500 series modules, including discontinued and hard-to-source variants. Our sourcing process covers: verified surplus stock from decommissioned plant assets, factory-refurbished units with full functional restoration, and new-old-stock (NOS) units with original MTL Instruments packaging and documentation. All units are traceable to original manufacturer certification records where available. For long-term maintenance contracts and scheduled outage kitting, DriveKNMS provides advance reservation and consignment stocking arrangements.

Quality Control for the MTL5500 Range

MTL5500 modules incorporate complex backplane bus interfaces, galvanic isolation barriers, and precision analog signal chains that require function-specific test procedures beyond standard continuity checks. DriveKNMS applies the following QC protocol to all MTL5500 units processed:

• IS barrier integrity test: verification of Zener diode clamp voltage and current-limiting resistor values against MTL published IS entity parameters
• Galvanic isolation test: hi-pot testing at rated isolation voltage (typically 1.5 kV rms) between input, output, and power circuits
• Analog accuracy verification: end-to-end signal injection at 4 mA, 12 mA, and 20 mA with output measurement against ±0.1% FS specification
• HART signal transparency test (for HART-capable variants): superimposed FSK signal pass-through verification at 1200 baud
• Temperature coefficient check: signal accuracy verification across 0–55°C ambient range
• Visual and mechanical inspection: terminal block integrity, module locking tab function, label legibility, and connector pin condition