MTL5082 MTL5000 Series RTD Isolated Repeater

Product Overview

The MTL5082 connects to resistance temperature devices in hazardous areas. It works with 2-, 3-, or 4-wire RTDs. The MTL5082 isolates the RTD signal and repeats it to safe area monitors. This module is intended primarily for Pt100 3-wire RTDs.

You can use the MTL5082 as an alternative to the MTL5074. It suits applications where a resistance input is preferred over 4-20mA. The design offers ease of use and excellent repeatability. Switches on top select the wiring configuration.

Technical Specifications

The MTL5082 provides one isolated channel. It operates with Zone 0 and Div. 1 hazardous locations. Below are the complete technical parameters.

• Manufacturer: MTL (Eaton)

• Product Type: RTD Isolated Repeater / Resistance Transmitter

• Series: MTL5000 Series

• Number of Channels: One

• Location of RTD: Zone 0, IIC, T4; Div.1, Group A

• Resistance Source: 2-, 3-, or 4-wire RTDs to BS 1904/DIN 43760 (100Ω at 0°C)

• Resistance Range: 10Ω to 400Ω

• RTD Excitation Current: 200μA nominal

• LED Indicator: Green (power and status)

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

Output Configuration

The MTL5082 output is independent of the input wiring mode. You can use 2, 3, or 4 wires on the safe-area side. The output range matches the input range. Output works with a 100μA to 5mA source. This flexibility simplifies system integration.

Switch Selection for RTD Wiring

Switches located on top of the MTL5082 select the wiring configuration. Factory default setting is 3-wire mode. You can change to 2-wire or 4-wire as needed. Always power down the MTL5082 before changing switches. Verify your RTD type before selection.

Temperature Drift and Response Time

The MTL5082 maintains stable performance across temperature changes. Temperature drift is ±10mΩ/°C typical. This equals 0.01%/°C at 100Ω reference. Response time reaches within 4% of final value within 1 second. This speed suits most temperature monitoring applications.

Open-Circuit Detection

The MTL5082 includes safety drive for open-circuit sensors. When an open circuit occurs, the output drives upscale. Nominal upscale value is 420Ω. This clearly indicates a sensor fault condition. Your monitoring system can detect this out-of-range value easily.

Terminal Assignments

The MTL5082 has clearly marked terminals for easy wiring. Below is the terminal function table.

Power Requirements

The MTL5082 consumes moderate current. Below are the power requirements at different supply voltages.

• At 24V: 55mA

• At 20V: 65mA

• At 35V: 45mA

Maximum power dissipation within the MTL5082 varies with supply voltage.

• At 24V: 1.4W

• At 35V: 1.6W

Low dissipation allows mounting multiple units in a single cabinet. The green LED indicates power and normal operation.

Safety Description (Entity Parameters)

The MTL5082 has two safety description groups. Use the correct group for your wiring configuration.

Terminals 1 and 3 only:

• Uo = 1.1V

• Io = 4mA

• Po = 1mW

These terminals meet EN50020:1994 clause 5.4 for simple apparatus. They connect into any IS loop with open circuit voltage not exceeding 10V. For higher voltages, contact MTL for guidance.

Terminals 1, 3, 4, and 5 combined:

• Uo = 6.6V

• Io = 27mA

• Po = 50mW

Wire Independence Feature

The MTL5082 has a unique wire independence feature. The number of wires on the safe-area side is independent of the hazardous-area side. You can use 2-wire hazardous connection with 3-wire safe connection. This flexibility solves wiring mismatches between field and panel.

Installation Guidance

Follow these steps to install the MTL5082 correctly.

1. Mount the Unit: Secure the MTL5082 on a DIN rail in a safe area.

2. Set Wiring Switches: Select 2, 3, or 4-wire mode for your RTD.

3. Connect RTD: Wire your Pt100 or other RTD to terminals 1,3,4,5.

4. Connect Output: Wire the MTL5082 output to your monitoring system.

5. Apply Power: Connect 20-35V dc to terminals 13 and 14.

6. Check Green LED: Verify power and status indicator is on.

7. Verify Reading: Compare output resistance with actual RTD value.

Do not exceed 35V dc supply voltage. Use twisted pair cables for RTD connections. Keep RTD wires away from power cables.

Package Contents

• One MTL5082 RTD isolated repeater unit

• One DIN rail mounting clip (attached)

• One top-mounted switch assembly (factory installed)

• One product identification label

• One installation instruction sheet

• One anti-static protective bag

Frequently Asked Questions (FAQ)

Q1: Can the MTL5082 work with non-Pt100 RTDs?
A1: Yes, the MTL5082 works with any RTD from 10Ω to 400Ω range. Calibration is for Pt100 at 100Ω. Other RTD types may have reduced accuracy.

Q2: What is the difference between MTL5082 and MTL5074?
A2: The MTL5082 provides direct resistance output. The MTL5074 provides 4-20mA output. Use MTL5082 when your monitor accepts resistance input directly.

Q3: How do I test the open-circuit detection feature?
A3: Disconnect one RTD wire from the MTL5082 input. Output should go upscale to approximately 420Ω. Reconnect the wire and output returns to normal.

Q4: Can I use the MTL5082 with a 2-wire RTD only?
A4: Yes, set the top switch to 2-wire mode. Connect the RTD to terminals 1 and 3 only. Leave terminals 4 and 5 unconnected on the MTL5082.

Q5: What is the maximum cable length for the RTD input?
A5: Maximum length depends on cable resistance and noise. Keep total lead resistance below 10Ω per wire. The MTL5082 200μA excitation works well with most installations up to 100 meters.