Eaton MTL7761PAC 2-Channel Intrinsic Safety Barrier with Strain-Gauge Bridge

The MTL7761PAC is a high-performance 2-channel shunt-diode safety barrier (Zener barrier) from Eaton's Crouse-Hinds series MTL7700 range, specifically engineered for strain-gauge bridge circuits, load cells, and Wheatstone bridge applications requiring intrinsic safety protection in hazardous areas.

The "PAC" suffix indicates the power bus version, distinguishing it from the standard MTL7761AC model. This variant is designed for use with bussed power feed systems, reducing cabling requirements.

• 2-Channel Efficiency: Two independent intrinsically safe channels in a single compact housing — protects two field devices while using minimal panel space
• Strain-Gauge Bridge Optimization: Specifically designed for strain-gauge bridge circuits and load cell applications — provides the precise voltage and current limiting required for Wheatstone bridge measurements in hazardous areas
• 9 V Working Voltage: Provides safe voltage limiting for strain-gauge bridge circuits, preventing ignition under fault conditions
• 350 Ω End-to-End Resistance: Matches the impedance requirements of typical strain-gauge bridge circuits and load cells
• 26 mA Maximum Current: Adequate current handling for strain-gauge bridge excitation and signal measurement
• Power Bus (PAC) Capability: The PAC version integrates with MTL7798 power feed module for bussed power distribution — reduces cabling requirements and installation costs
• Removable Terminals: Unique removable terminal blocks for easy cabling and maintenance — simplifies installation and replacement without rewiring
• Ultra-Slim DIN Rail Mounting: Compact 12.6 mm width for standard 35 mm DIN rail installation, saving valuable panel space
• Angled Wire Entry: Wire entry is angled to assist wiring within limited space enclosures
• Dual-Stage Protection: Two stages of pulse-tested Zener diodes and an 'infallible' terminating resistor ensure continued safety if either stage should fail. No active output current limiting circuits are employed — pure passive design for maximum reliability
• Wide Operating Temperature: Functions reliably from -20 °C to +60°C

The MTL7761PAC is a passive shunt-diode safety barrier that operates on the Zener barrier principle. It limits both voltage and current that can be delivered to a hazardous area circuit under fault conditions.

• Voltage limiting: Zener diodes clamp the output voltage to a safe level (9 V) if the safe-area voltage rises above normal operating levels
• Current limiting: A series resistor (350 Ω) limits fault current to a safe value (26 mA)
• Fusing: Internal 50 mA fuses provide backup protection under severe fault conditions — two stages of voltage limitation ensure continued safety if either stage should fail
• Grounding: The barrier requires a connection to a high-integrity earth ground to function properly
• No active output current limiting circuits are employed — pure passive design for maximum reliability

• When used in conjunction with the MTL7798 power feed module, the MTL7761PAC provides a fully protected, electronically fused supply to many barriers with no additional wiring required
• Bussed power reduces cabling requirements and installation costs

The MTL7761PAC is specifically designed for strain-gauge and load cell applications in hazardous area installations:

• Strain-gauge bridge sensors (full Wheatstone bridge configuration)
• Load cells (compatible with 350 Ω bridges)
• Torque sensors
• Pressure sensors based on strain-gauge technology
• Weighing systems in hazardous areas
• Tension detectors

• Optimized for Strain-Gauge Bridges — Unlike general-purpose safety barriers, the MTL7761PAC is specifically designed for strain-gauge bridge circuits and load cells, providing the precise 9 V, 350 Ω, 26 mA characteristics required for accurate measurement in hazardous areas.
• Power Bus Capability — The PAC version integrates with MTL7798 power feed module for bussed power distribution, significantly reducing cabling requirements and installation costs compared to standard barriers.
• 2-Channel Efficiency — With two independent channels in a single compact 12.6 mm housing, the MTL7761PAC protects two field devices while using minimal panel space.
• Unique Removable Terminals — Unlike competitors, the MTL7761PAC features removable terminal blocks that simplify cabling, maintenance, and barrier replacement without rewiring — a unique feature of the MTL7700 series.
• Angled Wire Entry — Wire entry is angled to assist wiring within limited space enclosures, making installation easier in crowded control cabinets.
• Dual-Stage Protection — Each channel contains two stages of pulse-tested Zener diodes and an 'infallible' terminating resistor. In the event of an electrical fault, the diodes limit voltage and the resistor limits current. The two stages of voltage limitation ensure continued safety if either stage should fail.
• Proven MTL7700 Series Reliability — The MTL7700 series has been the industry standard for shunt-diode safety barriers for decades, trusted globally for intrinsic safety applications. No active output current limiting circuits are employed — pure passive design for maximum reliability.
• Global Approvals — Certified for use in major industrial markets including ATEX (Europe) and IECEx (international), the MTL7761PAC simplifies global equipment standardization.
• Simple Installation — DIN rail mounting, clearly labeled terminals, removable terminal blocks, and compact 12.6 mm width make installation quick and intuitive.

• A high-integrity earth ground connection is mandatory for proper Zener barrier operation
• Do not install in areas where condensation may occur
• The barrier must be installed in a safe area (non-hazardous location)
• Maximum cable parameters for IIC gas group apply to field wiring
• For bussed power applications, use with MTL7798 power feed module

Contact our sales team for volume pricing, datasheet downloads, or technical application support.

The MTL7700 series offers a complete range of shunt-diode safety barriers for all intrinsic safety applications.