Eaton MTL MTL7758+ 7700 Series Digital Switch Safety Barrier ATEX Certified Hazardous Area
The MTL7758+ is a high-performance 2-channel shunt-diode safety barrier (Zener barrier) from Eaton's Crouse-Hinds series MTL7700 range, specifically engineered for gas detectors and high-current/low-voltage 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 rated supply voltage of 7.5V DC, safety description of 7.5V, 10 Ω, 750mA, and positive polarity configuration, the MTL7758+ is the ideal solution for protecting gas detectors, catalytic bead sensors, and other high-current field devices 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.
| Code Segment | Meaning |
|---|---|
| MTL | MTL Instruments Group (now Eaton) |
| 77 | MTL7700 series — Shunt-diode safety barriers |
| 58 | Specific barrier configuration for high-current/low-voltage applications |
| + | Positive polarity configuration |
The "+" suffix indicates positive polarity, distinguishing it from the negative polarity version MTL7758-.
- Gas Detector Optimization: Specifically designed for gas detection applications — catalytic bead and infrared gas sensors requiring higher operating currents
- High-Current/Low-Voltage Design: Safety description of 7.5V, 10 Ω, 750mA — ideal for devices requiring up to 750mA at low voltage
- 2-Channel Efficiency: Two independent intrinsically safe channels in a single compact housing — protects two field devices while using minimal panel space
- Positive Polarity Configuration: Designed for positive ground applications — common in many industrial control systems
- IIC Gas Group Certification: Certified for the most hazardous IIC gas groups (hydrogen, acetylene) — suitable for use in Zone 0, 1, and 2 explosive atmospheres
- Removable Terminals: 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: Integrated bussed power distribution reduces cabling requirements — 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: Contains two stages of pulse-tested Zener or forward-connected diodes and an 'infallible' terminating resistor for maximum reliability
- Digital Output Range: Part of Eaton MTL's digital output range — designed for switching and power applications in hazardous areas
- Global Approvals: CCC Ex (China valid until 2030-09-01), ATEX, IECEx, CSA, FM certifications for international installation flexibility
| Parameter | Value |
|---|---|
| Safety Description | 7.5 V, 10 Ω, 750 mA |
| Rated Supply Voltage DC | 7.5 V DC |
| End-to-End Resistance (Max) | 17 Ω |
| Maximum Current | 750 mA |
| Terminal Voltage @ 10 µA | 6.0 V (min) |
| Terminal Voltage @ 20mA | 7.3 V (max) |
| Fuse Rating | 200 mA |
| Typical Application | Gas detectors |
| Parameter | Value |
|---|---|
| Gas Groups | IIC, IIB, IIA |
| Zones | Zone 0, 1, 2 |
| ATEX/IECEx Rating | II (1) GD [Ex ia] IIC |
| Parameter | Value |
|---|---|
| Width | 12.6 mm |
| Height | 90 mm |
| Depth/Length | 105 mm |
| Weight | 0.500 kg |
| Enclosure Material | Polycarbonate |
| Mounting | 35 mm T-section DIN rail (EN 60715) |
| Terminals | Removable screw terminals, colour-coded |
| Parameter | Value |
|---|---|
| Minimum Operating Temperature | -20°C |
| Maximum Operating Temperature | +60°C |
| Degree of Protection | IP20 |
Certificate 2020322316002402 is valid until September 1, 2030.
The MTL7758+ 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 (7.5V) if the safe-area voltage rises above normal operating levels
- Current limiting: A series resistor (10Ω) limits fault current to a safe value (750mA)
- Fusing: A 200mA fuse protects the diodes, and the two stages of voltage limitation ensure continued safety if either stage should fail
- Positive polarity: The barrier is designed for positive ground applications — common in gas detector installations
- 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 MTL7758+ is specifically designed for gas detection and high-current/low-voltage protection in hazardous area installations:
| Industry | Application |
|---|---|
| Oil & Gas | Catalytic bead gas detector protection on offshore platforms and refineries — LEL monitoring |
| Chemical Processing | Toxic and combustible gas detection systems in explosive atmospheres |
| Petrochemical | Fixed gas detection systems for H2S, CH4, and other hazardous gases |
| Mining | Methane gas detector protection in underground mining environments |
| Water/Wastewater | Digester gas monitoring — H2S and CH4 detection |
| Industrial Safety | Area gas monitoring systems requiring high current for sensor operation |
- Catalytic bead gas detectors (pellistor type) — requiring 200-300mA operating current
- Infrared (IR) gas sensors
- Electrochemical gas sensors
- High-current/low-voltage sensors and actuators
- Combustible gas detectors requiring higher power
Optimized for Gas Detectors — Specifically designed for gas detection applications with safety description 7.5V, 10 Ω, 750mA. The low 10Ω resistance and high 750mA current capability make it ideal for catalytic bead and infrared gas sensors.
2-Channel Efficiency — With two independent channels in a single compact 12.6 mm housing, the MTL7758+ protects two field devices while using minimal panel space — just 6.3 mm per channel.
High-Current/Low-Voltage Design — The MTL7758+ is specifically engineered for applications requiring high current at low voltage — distinguishing it from general-purpose 28V barriers.
Unique Removable Terminals — Unlike competitors, the MTL7758+ features removable terminal blocks that simplify cabling, maintenance, and barrier replacement without rewiring.
Global Approvals — Certified for use in major industrial markets including CCC Ex (China valid to 2030), ATEX (Europe), IECEx (international), CSA (North America), and FM (USA).
| Parameter | Detail |
|---|---|
| Mounting | Standard 35 mm T-section DIN rail (EN 60715) |
| Terminals | Removable screw terminals, colour-coded (blue for hazardous area) |
| Grounding | High-integrity earth connection made simultaneously when clipping onto DIN rail |
| Wire Entry | Angled to assist wiring in limited space enclosures |
| Terminal Capacity | Accommodates conductors up to 2.5 mm² |
| Clearance | Minimal — 12.6 mm width enables high-density installation |
| Operating Position | Any orientation |
- 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
- Recommended for use with nominal 6V power supplies
- Positive polarity configuration — ensure correct orientation for your control system
- Suitable for catalytic bead and infrared gas detectors
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