EATON MTL MTL5573 Temperature Converter Isolator – MTL5000 Series

MTL5573 – Three-Port Galvanic Temperature Converter Isolator for Hazardous-Area Signal Conditioning

The EATON MTL MTL5573 occupies a well-defined position in the intrinsically safe signal chain: it accepts a raw sensor signal from a field device located in a classified hazardous area, performs linearisation and conversion, and delivers a calibrated 4–20 mA analog output to a safe-area DCS or PLC analog input card. Unlike passive zener barriers that rely on a shared earth reference, the MTL5573 employs three-port galvanic isolation — separating the hazardous-area input circuit, the safe-area output circuit, and the 24 V DC supply rail into three electrically independent domains. This architecture eliminates ground-loop currents that would otherwise introduce a DC offset error into the temperature measurement, a failure mode that is particularly destructive in long cable runs exceeding 500 m.

The module accepts RTD inputs (Pt100 three-wire, Pt1000), thermocouple types J, K, T, E, R, S, and B, millivolt sources, and direct resistance measurements — all selectable via front-panel DIP switches without any external configuration tool. This input universality means a single MTL5573 spare covers the majority of temperature sensor types deployed across a typical process plant, reducing the minimum spare-parts holding and simplifying procurement.

ATEX and IECEx certification to intrinsic safety category “ia” permits direct wiring to sensors installed in Zone 0 — the most stringent hazardous area classification, where an explosive atmosphere is present continuously. The module’s entity parameters (Ui, Ii, Pi, Ci, Li) are fully documented in the ATEX certificate, allowing system designers to calculate the combined capacitance and inductance of the field cable and verify compliance with IEC 60079-11 without additional calculation overhead.

Mechanically, the MTL5573 is a plug-in module designed for the MTL5000 DIN rail carrier system. The plug-in architecture allows field replacement in under 60 seconds without disturbing field wiring — the carrier retains all terminal connections while the module is extracted and reinserted. This hot-swap capability is critical in continuous-process industries where a planned shutdown to replace a faulty isolator is economically unacceptable. The module’s compact 17.5 mm pitch allows high-density marshalling in restricted panel spaces.

Supply voltage tolerance of 9.6–35 V DC accommodates the full range of 24 V DC rail conditions encountered in field junction boxes, including brownout conditions during motor starting transients. The active 4–20 mA output sources loop current independently, eliminating the need for an external loop power supply on the receiving instrument side and simplifying the safe-area wiring design.

All units supplied by siemensplc.com are sourced from verified distribution channels. Each module is inspected for label authenticity, housing integrity, and certification marking before dispatch. Traceability documentation is available upon request for regulated industries including pharmaceutical, nuclear, and offshore oil and gas.

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Technical Parameters

Hardware Logical Analysis

The MTL5573’s internal architecture is built around a DC/DC converter that generates isolated power rails for the input and output stages from the single 24 V DC supply. This converter operates at a switching frequency above the audible range and is filtered to prevent conducted emissions from coupling back onto the supply rail — a requirement under EN 61000-6-4 for industrial environments with shared DC bus architectures.

The input stage employs a precision excitation current source for RTD measurements. For Pt100 three-wire connections, the module uses a matched current source on the sense wire to cancel the resistance of the field cable, achieving a cable resistance rejection of typically ±0.1°C per ohm of lead resistance — a specification that matters in installations where field cable runs exceed 100 m and conductor resistance is non-negligible.

Thermocouple inputs are handled by a cold-junction compensation (CJC) circuit located at the module’s terminal block. The CJC sensor measures the terminal temperature and applies a correction to the thermocouple EMF before linearisation, maintaining measurement accuracy across the full -20°C to +60°C ambient operating range without requiring an isothermal terminal block in the marshalling cabinet.

EMC performance is achieved through a combination of transformer-based galvanic isolation (which inherently blocks common-mode interference), transient suppression diodes on all external-facing terminals, and a PCB layout that separates high-frequency switching nodes from the precision analog measurement circuitry using a ground plane partition strategy. The result is a module that maintains specified accuracy in environments with radiated field strengths up to 10 V/m (IEC 61000-4-3, Severity Level 3) — a condition routinely encountered near VFD panels and radio communication equipment in process plants.

The output stage drives the 4–20 mA loop with a compliance voltage sufficient to drive loads up to 600 Ω, accommodating the combined resistance of long cable runs and the input impedance of the receiving AI card without output saturation.

System Integration Benefits

• Deterministic signal latency: The analog 4–20 mA output updates continuously with a response time of < 500 ms for step changes, ensuring that DCS scan cycles receive a current representation of the process temperature without buffering delays introduced by digital fieldbus protocols.
• Ground-loop immunity: Three-port galvanic isolation eliminates the DC offset errors caused by potential differences between hazardous-area and safe-area earth references — a common source of unexplained measurement drift in plants with multiple earthing systems.
• Zone 0 direct connection: ATEX “ia” certification removes the need for an intermediate zener barrier between the sensor and the isolator, reducing the component count in the signal chain and eliminating one potential failure point.
• Universal sensor compatibility: A single module type covers RTD, thermocouple, mV, and resistance inputs, allowing maintenance teams to stock one spare part number instead of four — directly reducing working capital tied up in spare parts inventory.
• Hot-swap field replacement: The plug-in module design allows replacement under power without disturbing field wiring, reducing mean time to repair (MTTR) to under five minutes in a trained technician’s hands.
• Backward carrier compatibility: Full mechanical and electrical compatibility with existing MTL5000 DIN rail carriers means the MTL5573 can replace older MTL5000 series temperature converters without panel modification or rewiring.
• Wide supply tolerance: The 9.6–35 V DC supply range accommodates voltage sag during motor starting events and allows operation from both 12 V and 24 V DC bus architectures without a dedicated voltage regulator.
• Diagnostic transparency: Output current clamping behavior (output drives to 3.6 mA on sensor break, 21 mA on sensor short, depending on configuration) provides unambiguous fault indication to the DCS, enabling the control system to distinguish a process temperature at range limits from a wiring fault — a distinction that passive barriers cannot provide.
• Reduced panel footprint: The 17.5 mm module pitch allows 32 channels per 600 mm DIN rail section, achieving a channel density comparable to fieldbus marshalling panels while retaining the simplicity of conventional 4–20 mA wiring.
• Regulatory compliance path: ATEX and IECEx dual certification satisfies both European and international project specifications from a single part number, avoiding the cost and lead time of sourcing region-specific variants.

Quality Assurance & Global Logistics

Every MTL5573 unit dispatched from our Xiamen, China facility is an authentic EATON MTL product sourced through verified supply channels. Prior to dispatch, each module undergoes a structured inspection protocol: visual examination of the housing and certification labels, verification of the ATEX/IECEx marking against the declared certificate number, and functional confirmation of the input-to-output signal path. Anti-static packaging with humidity indicator cards is used for all shipments to protect the precision analog circuitry during transit.

Logistics from Xiamen are optimised for both speed and documentation completeness. Standard international shipments are dispatched via DHL Express or FedEx International Priority, with typical transit times of 3–5 business days to Europe, 4–6 days to the Americas, and 2–3 days to Southeast Asia. For projects requiring expedited delivery, same-day dispatch is available for orders confirmed before 14:00 CST. Commercial invoice, packing list, and certificate of origin are provided with every shipment. For regulated industries, a 12-month warranty certificate and traceability documentation are available upon request at no additional charge.

Customs classification: HS Code 8533.40 (electrical resistors, including rheostats and potentiometers) or 8543.70 as applicable — our logistics team will advise the correct classification for your destination country to avoid customs delays.

Contact Information

Email: [email protected]
WhatsApp: +86 18359268345
Web: siemensplc.com
Location: Xiamen, China
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