Product Overview

The MTL5074 belongs to the MTL5000 series of isolation converters. Specifically, it is a single-channel device for temperature sensors in hazardous areas. Furthermore, this unit accepts thermocouple, EMF, or RTD input signals. Finally, the converter provides a standard 4-20mA output for safe-area control systems.

Common applications for the MTL5074 include temperature monitoring in Zone 0 hazardous locations. For instance, it connects thermocouples or RTDs to PLCs and DCS systems. Moreover, the unit supports Div.1, Group A hazardous locations. Consequently, it suits the most demanding explosive environments.

Technical Specifications

The MTL5074 accepts multiple input types for broad compatibility. Specifically, the signal source includes Types J, K, T, E, R, S, B, or N thermocouples. Furthermore, it accepts 2, 3, or 4-wire platinum RTDs to BS 1904/DIN43760 (100Ω at 0°C). Finally, direct EMF input from -75 to +75mV is also supported.

Key Input Parameters

• Input signal range: -75 to +75mV, or 0 to 400Ω (Input impedance 10MΩ)

• Input signal span: 3 to 150mV, or 10 to 400Ω

• RTD excitation current: 200µA nominal

• Input connections: Terminals 1 (-ve), 3 (+ve) for THC/EMF/RTD

• RTD additional connections: Terminal 4 (3-wire -ve), Terminal 5 (4-wire +ve)

Cold Junction Compensation

• Cold junction compensation: Automatic or selectable

• Cold junction compensation error: ≤1.0°C

• For thermocouples requiring CJC, order the HAZ-CJC plug (includes integral CJC sensor)

Noise Rejection Specifications

• Common mode rejection: 120dB for 240V at 50Hz or 60Hz

• Series mode rejection: 40dB for 50Hz or 60Hz

• Therefore, the MTL5074 performs well in electrically noisy environments

Calibration Accuracy (at 20°C)

The MTL5074 accuracy includes hysteresis, non-linearity, and repeatability:

• mV/THC input: ±15µV or ±0.05% of input value (whichever is greater)

• RTD input: ±80mΩ

• Output: ±11µA

Temperature Drift (typical)

• mV/THC input: ±0.003% of input value/°C

• RTD input: ±7mΩ/°C

• Output: ±0.6µA/°C

Output and Power Parameters

• Output range: 4 to 20mA nominal (direct or reverse acting)

• Maximum load resistance: 600Ω

• Safety drive on sensor burnout: Upscale, downscale, or off (selectable)

• Output connections: Terminal 11 (-ve), Terminal 12 (+ve)

Power Requirements (with 20mA signal)

• 68mA at 24V

• 82mA at 20V

• 52mA at 35V

• Power dissipation: 1.5W at 24V, 1.6W at 35V

LED Indicator

• Green LED: One provided for power and status indication

Isolation and Safety

• Isolation voltage: 250V ac between safe-area, hazardous-area, and power supply circuits

• Suitable for Zone 0, IIC, T4 hazardous areas

• Suitable for Div.1, Group A hazardous locations

Terminal Functions

The MTL5074 uses clearly labeled terminals for easy wiring:

• Terminal 1: THC/EMF/RTD input –ve

• Terminal 3: THC/EMF/RTD input +ve

• Terminal 4: 3-wire RTD input –ve

• Terminal 5: 4-wire RTD input +ve

• Terminal 11: Output –ve (4-20mA)

• Terminal 12: Output +ve (4-20mA)

• Terminal 13: Supply –ve

• Terminal 14: Supply +ve

Standard Configuration

The MTL5074 ships with the following default settings:

• Input type: RTD, 3-wire

• Linearisation: Enabled

• CJC compensation: Disabled

• Units: °C

• Damping/Smoothing value: 0 seconds / 0 seconds

• Output zero: 0°C

• Output span: 250°C

• Tag and description fields: Blank

• Open circuit alarm: High (upscale)

• Transmitter failure alarm: Low (downscale)

• Cj failure alarm: Low (downscale)

• Line frequency: 50Hz

Configurator Requirements

To reconfigure the MTL5074, you need:

• A personal computer running MTL PCS45 software

• A PCL45 interface cable

Ordering Options

Specify one of the following when ordering:

• MTL5074: Includes HAZ-CJC signal plug (with internal CJC sensor). For use with thermocouple, mV, or RTD inputs.

• MTL5074-RTD: Includes standard HAZ1-3 signal plug. For use with mV or RTD inputs. (Can be used with thermocouples if HAZ-CJC plug is fitted separately.)

• HAZ-CJC: Hazardous-area signal plug for terminals 1 to 3 including cold-junction compensation sensor.

Installation Guidelines

When installing the MTL5074, follow these important steps:

• First, mount the unit on standard DIN rail in a safe area cabinet

• Next, connect the power supply to terminals 13 (-ve) and 14 (+ve)

• Then, wire your thermocouple or RTD sensor to the appropriate input terminals

• Finally, connect the 4-20mA output to your control system (terminals 11 and 12)

The MTL5074 requires the correct signal plug for thermocouple operation. Specifically, use the HAZ-CJC plug for cold junction compensation. Furthermore, use shielded cable for all sensor inputs. Consequently, this ensures optimal measurement accuracy.

Packing List

• 1 x MTL5074 Temperature Converter Module

• 1 x Signal plug (HAZ-CJC or HAZ1-3 based on order option)

• 1 x DIN rail mounting clip (factory installed)

• 1 x Terminal label sheet

• 1 x Configuration instruction manual

Frequently Asked Questions (FAQ)

Q: What is the difference between MTL5074 and MTL5074-RTD?
A: The MTL5074 includes the HAZ-CJC plug with integral cold junction compensation sensor. The MTL5074-RTD includes the standard HAZ1-3 plug without CJC. Therefore, use MTL5074 for thermocouple applications and MTL5074-RTD for pure RTD or mV applications.

Q: Can the MTL5074 be used with 2-wire RTD sensors?
A: Yes. The MTL5074 accepts 2-wire, 3-wire, and 4-wire platinum RTDs. For instance, use terminals 1 and 3 for 2-wire RTDs. Furthermore, add terminal 4 for 3-wire lead compensation. Consequently, you can achieve accurate measurements with any RTD configuration.

Q: What is the maximum load resistance for the MTL5074 output?
A: The MTL5074 can drive a maximum load resistance of 600Ω. Specifically, this allows long cable runs to your control system. Therefore, calculate your total loop resistance before installation to ensure proper operation.

Q: What software is needed to configure the MTL5074?
A: The MTL5074 requires MTL PCS45 software running on a personal computer. Specifically, you also need the PCL45 interface cable. Furthermore, the software allows selection of thermocouple types, ranging, linearisation, and alarm settings. Therefore, keep a configuration PC available for initial setup.