MTL 5018 Thermocouple Isolator | TC Input, 4-20mA Output, IS, DIN Rail, ATEX/IECEx/FM

MTL 5018 Thermocouple Isolator | TC Input, 4-20mA Output, IS, DIN Rail, ATEX/IECEx/FM

MTL 5018 thermocouple isolator/transmitter specifications. TC (J,K,T,E,R,S,B,N) input, 4-20mA output, intrinsic safety, 24V DC, DIN rail. ATEX/IECEx/FM approved.

Product Overview

The MTL 5018​ is a single-channel thermocouple (TC) isolator and transmitter​ from MTL's 5000 series. It accepts a wide range of thermocouple input types​ (J, K, T, E, R, S, B, N) from a hazardous area, provides intrinsic safety (IS) isolation, cold junction compensation (CJC), and linearization, and delivers a precision, isolated 4-20mA output​ to the safe-area control system. Certified for Zone 1 hazardous locations, it is the industry standard for converting and isolating thermocouple signals with high accuracy and reliability.

Technical Specifications

Note: Specifications are based on MTL 5000 series documentation. Always verify with the latest product datasheet for the specific region and model variant.

Key Features

• Wide Thermocouple Support:​ Compatible with all major industrial TC types (J, K, T, E, R, S, B, N).

• Integrated Cold Junction Compensation (CJC):​ Built-in, high-accuracy CJC sensor eliminates the need for external compensation.

• High Accuracy & Stability:​ ±0.1% accuracy with excellent noise rejection and low temperature drift.

• Intrinsic Safety Barrier:​ Certified for Zone 1/21, protecting equipment in hazardous areas.

• Built-in Linearization:​ Converts non-linear TC millivolt signal to a linear 4-20mA output per international standards.

• Easy Configuration:​ No software required; set up via onboard DIP switches for TC type, range, and burnout response.

• Compact Design:​ Only 12.5mm wide for high-density DIN rail installations.

• Comprehensive Diagnostics:​ Includes sensor burnout (open-circuit) detection with configurable failure mode.

• Galvanic Isolation:​ 500V isolation prevents ground loops and protects against transients.

• Global Hazardous Area Approvals:​ Suitable for international installations.

Supported Thermocouple Types & Standard Ranges

The specific 4mA (LRV) and 20mA (URV) points are selected via DIP switches, allowing customization within the TC's full range.

Principle of Cold Junction Compensation (CJC)

[Thermocouple in Process]-----(TC+ & TC- wires)----->[MTL 5018 Terminal Block]
              (T_process)                                     |
                                                              |
    Voltage measured = V_TC(T_process, T_cj) <---------------'
    Where T_cj = Temperature at the terminal block (Cold Junction).

    The MTL 5018:
    1. Measures the voltage from the TC wires.
    2. **Measures T_cj** using its internal CJC sensor.
    3. **Calculates the equivalent voltage at 0°C** using the TC standard table: V_TC(T_process, 0°C) = V_measured + V_TC(T_cj, 0°C).
    4. Linearizes this corrected voltage to the configured 4-20mA output.

The accuracy of the internal CJC sensor (±1°C) is critical to the overall measurement accuracy.

Entity Parameters (for Hazardous Area Loop Design)

Note: The connected thermocouple in the hazardous area is considered a "Simple Apparatus." Ensure the cable parameters (Cable, Lo) are within the allowed values for the IS loop.

DIP Switch Configuration Overview

Refer to the product manual for the exact DIP switch coding table, as it combines type and range selection.

Typical Applications

• High-Temperature Process Monitoring:​ Furnaces, kilns, reactors, and boilers in petrochemical, chemical, and metal industries.

• Combustion Control:​ Flame and exhaust gas temperature measurement.

• Heat Treatment & Forging:​ Temperature control in ovens and forges.

• Power Generation:​ Boiler tube, turbine, and stack gas temperature monitoring.

• Glass & Ceramics:​ Melting tank and lehr temperatures.

• Incinerators & Thermal Oxidizers:​ High-temperature process gas measurement.

• Any application​ requiring accurate, isolated temperature measurement from a thermocouple in a hazardous area.

Important Technical Notes

1. Thermocouple Wire:​ Must use the correct thermocouple extension wire or compensating cable​ matching the TC type (e.g., K-type wire for a K-type TC). Using incorrect wire introduces significant measurement errors.

2. Cold Junction Location:​ The 5018's internal CJC sensor compensates for temperature at its own terminals. Ensure the unit is mounted in a stable temperature environment, away from heat sources or drafts, for optimal CJC accuracy.

3. Sensor Certification:​ The thermocouple sensor (probe) in the hazardous area must be intrinsically safe certified or qualify as a "Simple Apparatus."

4. Loop Power:​ The device is loop-powered. Ensure the control system's 24V DC supply can drive the loop: Vsupply > (Vtx_min + V5018_drop + Iloop * Rload). The 5018 requires a minimum voltage to operate (check datasheet, typically ~12V).

5. Configuration is Critical:​ Incorrect DIP switch settings (TC type, range) are a common source of error. Double-check settings against the sensor and desired range.

6. Open-Circuit (Burnout) Detection:​ Configure the burnout response based on process safety. "Upscale" (high output) is standard to force an alarm on sensor break.

7. Noise Immunity:​ Use shielded, twisted pair thermocouple wire. Ground the shield at the 5018 end only​ (terminal provided). Do not ground at the sensor end in hazardous areas.

8. Calibration:​ For critical applications, periodic calibration of the entire loop (TC + 5018) is recommended. The 5018's input cannot be easily trimmed in the field without a precision millivolt source.

Note: This data sheet provides general specifications for the MTL 5018 thermocouple isolator/transmitter. For complete installation instructions, detailed DIP switch tables, wiring diagrams, intrinsic safety guidelines, and certification details, consult the official MTL 5000 Series Technical Manual​ and the product-specific data sheet. Always ensure the selected configuration matches the field sensor and process requirements.