MTL7761AC Eaton MTL Ex ia Single Channel 4-20mA Analog Current Loop Zener Safety Barrier

The MTL7761AC 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 and load cell applications requiring intrinsic safety protection in hazardous areas.

This passive device limits the voltage and current that can reach a hazardous area under fault conditions, preventing ignition of flammable atmospheres. With a safety description of 9V, 90 Ω, 100mA, the MTL7761AC is the ideal solution for protecting strain gauge bridges and load cells in Zone 0, 1, and 2 hazardous locations (gas groups IIC, IIB, IIA).

The device features a compact 12.6 mm width and standard DIN rail mounting for easy integration into existing control cabinets.

• Strain Gauge Bridge Optimization: Specifically designed for strain gauge bridge circuits and load cell applications — provides the precise voltage and current limiting required for accurate measurements in hazardous areas
• 2-Channel Efficiency: Two independent intrinsically safe channels in a single compact housing (just 6.3 mm per channel) — protects two field devices while using minimal panel space
• 9V, 90 Ω, 100mA Safety Description: Provides safe voltage and current limiting for strain gauge circuits, preventing ignition under fault conditions
• Non-Polarized AC Operation: The "AC" suffix indicates non-polarized operation for both AC and DC circuits — eliminates wiring errors and simplifies installation
• Removable Terminals — UNIQUE: Unique removable terminal blocks for easy cabling, maintenance, and loop disconnect by simply unplugging terminals from the side of the module — a UNIQUE feature of the MTL7700 series
• Bussed Power Capability — UNIQUE: Integrated bussed power distribution reduces cabling requirements. When used with the MTL7798 power feed module, provides a fully protected, electronically fused supply to many barriers with no additional wiring required — 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
• Ultra-Slim DIN Rail Mounting: Compact 12.6 mm width for standard 35 mm T-section DIN rail — simultaneously makes a reliable IS earth connection when clipped onto the rail
• Dual-Stage Protection: Each channel contains two stages of pulse-tested Zener or forward-connected diodes and an 'infallible' terminating resistor. The two stages of voltage limitation ensure continued safety if either stage should fail. No active output current limiting circuits are employed — pure passive design for maximum reliability
• Direct Replacement for MTL700 Series: Compatible terminal numbering and safety descriptions allow direct replacement of older MTL700 series barriers
• Global Approvals: CCC Ex (China valid until 2030-09-01), ATEX, IECEx, UL, CSA certifications for international installation flexibility

The MTL7761AC 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 or forward-connected diodes clamp the output voltage to a safe level (8.4V) if the safe-area voltage rises above normal operating levels
• Current limiting: A series resistor (90Ω) limits fault current to a safe value (100mA)
• Fusing: A fuse protects the diodes, and the two stages of voltage limitation ensure continued safety if either stage should fail
• Strain gauge application: Use to sense the bridge supply voltage in strain gauge bridge circuits
• No active output current limiting circuits: Pure passive design for maximum reliability
• Grounding: The barrier requires a connection to a high-integrity earth ground — made simultaneously when clipping onto standard T-section DIN rail

The MTL7761AC is specifically designed for strain gauge bridge protection in hazardous area installations:

• Strain gauge bridge sensors (full Wheatstone bridge configuration)
• Load cells
• Torque sensors
• Pressure sensors based on strain gauge technology
• Weighing systems in hazardous areas

• 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)
• Hazardous-area terminals are identified by blue labels
• For bussed power applications, use with MTL7798 power feed module
• Compatible with existing MTL700 range installations — direct replacement
• Use to sense the bridge supply voltage in strain gauge bridge circuits