MTL 787S+ Loop-Powered Isolator | 2-Wire, 4-20mA, 1:1, IS, FM/ATEX/IECEx Specs

MTL 787S+ Loop-Powered Isolator | 2-Wire, 4-20mA, 1:1, IS, FM/ATEX/IECEx Specs

MTL 787S+ loop-powered isolator specifications. 2-wire, 4-20mA, 1:1 isolation, 24V DC loop, intrinsic safety. FM/ATEX/IECEx approved for hazardous areas.

Product Overview

The MTL 787S+​ is a loop-powered, two-wire signal isolator​ from MTL's 787 series, designed for intrinsic safety applications​ in hazardous areas. This device provides 1:1 signal isolation​ for 4-20mA current signals, is powered directly from the 4-20mA loop, and carries FM, ATEX, and IECEx approvals​ for Zone 1 hazardous locations. The "787S+" designation indicates the standard 4-20mA model with enhanced features. This isolator protects control systems from ground loops and interference while providing safety isolation for field instruments in explosive atmospheres.

Technical Specifications

Note: Specifications are based on MTL 787+ series documentation. The "S+" suffix indicates standard 4-20mA model. Always verify with the latest product datasheet for your region.

Key Features

• Loop-Powered Operation:​ No separate power supply required - powered directly from 4-20mA signal

• 1:1 Isolation:​ Provides galvanic isolation between field and control systems

• Intrinsic Safety:​ Approved for Zone 1 hazardous locations

• High Accuracy:​ ±0.1% accuracy for precise signal transmission

• Low Voltage Drop:​ Only 5.5V at 20mA, maximizing available loop voltage

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

• Wide Temperature Range:​ -20°C to +60°C operation

• LED Indicator:​ Visual confirmation of loop operation

• Global Approvals:​ Certified for international hazardous area applications

• Maintenance-Free:​ No calibration or maintenance required

Entity Parameters (for Hazardous Area Design)

Note: The 787S+ is typically considered a "simple apparatus" when used within its electrical parameters.

Typical Wiring Configuration

Field Transmitter (Hazardous Area)
      |
      | 2-wire (4-20mA)
      |
   [787S+ Isolator]
      |
      | 2-wire (4-20mA)
      |
Control System (Safe Area)
      |
      | 24V DC Power Supply
      |
     Ground

Typical Applications

• Process Control:​ Isolation of 4-20mA signals from field transmitters in hazardous areas

• Temperature Monitoring:​ Isolation for RTD and thermocouple transmitters

• Pressure/Level Measurement:​ Signal isolation for pressure/level transmitters

• Flow Measurement:​ Isolation for flow transmitter signals

• Analytical Instruments:​ Signal conditioning for gas detectors and analyzers

• Motor Monitoring:​ Current signal isolation for motor protection devices

• Any application requiring​ intrinsic safety isolation for 4-20mA signals between Zone 1 and safe areas

Important Technical Notes

1. Loop Power Calculation:​ Ensure sufficient loop voltage: Total voltage ≥ (Transmitter voltage drop + Isolator voltage drop + Cable drop). Minimum 9V required at isolator.

2. System Certification:​ The entire intrinsically safe loop must be properly certified. Use only approved power supplies and field devices.

3. Grounding:​ The isolator does not require a dedicated ground for safety function, but proper grounding of the control system is essential for noise immunity.

4. Installation Location:​ Install in the safe area. The device provides isolation between hazardous area field devices and safe area control systems.

5. Wiring Practices:​ Use twisted pair cables for noise immunity. Maintain separation between intrinsically safe and non-intrinsically safe wiring (minimum 50mm).

6. Voltage Limitations:​ Do not exceed 30V DC maximum loop voltage. Ensure power supply is current-limited to prevent damage.

7. LED Indicator:​ Green LED indicates sufficient loop current (> approximately 3.5mA). No LED indicates open circuit or insufficient current.

8. Temperature Considerations:​ Ensure ambient temperature remains within -20°C to +60°C range. High temperatures can affect accuracy and longevity.

9. Certification Compliance:​ Verify that the isolator's certifications (FM, ATEX, IECEx) match the hazardous area classification and gas groups of your specific application.

Note: This data sheet provides general specifications for the MTL 787S+ loop-powered isolator. For complete installation guidelines, certification details, wiring diagrams, and safety instructions, consult the official MTL 787+ Series Technical Manual. Always verify that the product configuration and certifications match your specific application requirements.