Eaton MTL MTL7728P+ ATEX Current Loop Barrier
Product Overview
The MTL7728+ is a high-performance 1-channel shunt-diode safety barrier (Zener barrier) from Eaton's Crouse-Hinds series MTL7700 range, specifically engineered for analogue and digital I/O 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 28 V DC, safety description of 28 V, 300 Ω, 93 mA, and positive polarity configuration, the MTL7728+ is the ideal solution for protecting controller outputs, solenoids, proximity detectors, and switch inputs 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.
Model Number Decoding: MTL7728+
| Code Segment |
Meaning |
| MTL |
MTL Instruments Group (now Eaton) |
| 77 |
MTL7700 series — Shunt-diode safety barriers |
| 28 |
Specific barrier configuration for general-purpose I/O applications |
| + |
Positive polarity configuration |
The "+" suffix indicates positive polarity, distinguishing it from negative polarity and AC versions. This model is the direct replacement for the discontinued MTL728+ from the MTL700 range.
Key Features & Benefits
- 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
- 1-Channel General Purpose I/O: Single channel rated for 93 mA switching current — ideal for protecting controller outputs, solenoids, proximity detectors, and switch inputs
- 28 V Working Voltage: Provides safe voltage limiting for analogue/digital circuits, preventing ignition under fault conditions
- 300 Ω End-to-End Resistance: Matches typical loop resistance requirements for 4-20 mA signal circuits while ensuring intrinsic safety compliance
- 93 mA Maximum Current: Adequate current handling for most field instrumentation including transmitters, sensors, and switch inputs
- Replaceable Secondary Fuses: Features secondary replaceable fuses — useful where there is the possibility of faults occurring during commissioning
- Removable Terminals: Unique removable terminal blocks for easy cabling, maintenance, and loop disconnect by simply unplugging terminals from the side of the module
- Bussed Power Capability: Integrated bussed power distribution reduces cabling requirements when used with the MTL7798 power feed module
- Angled Wire Entry: Wire entry is angled to assist wiring within limited space enclosures
- Ultra-Slim DIN Rail Mounting: Compact 12.6 mm width for standard 35 mm T-section DIN rail
- Dual-Stage Protection: Contains two stages of pulse-tested Zener or forward-connected diodes and an 'infallible' terminating resistor
- Direct Replacement for MTL700 Series: Compatible terminal numbering and safety descriptions allow direct replacement of older MTL700 series barriers
- Global Approvals: ATEX, IECEx, UL, CSA, FM, KOSHA (Korea), and LR Marine certifications for international installation flexibility
Technical Specifications
General Specifications
| Parameter |
Value |
| Manufacturer |
Eaton (Crouse-Hinds series MTL) |
| Series |
MTL7700 Range |
| Product Model |
MTL7728+ |
| Product Type |
Zener Barrier (Shunt-Diode Safety Barrier) |
| Number of Channels |
1 (single-channel) |
| Polarity |
Positive (+) |
Electrical Ratings
| Parameter |
Value |
| Safety Description |
28 V, 300 Ω, 93 mA |
| Rated Supply Voltage DC |
28 V DC |
| Safety Voltage Maximum |
26 V dc |
| Safety Current Resistance |
300 Ω |
| Switching Current (Maximum) |
93 mA |
| Matched Power Output |
0.651 W |
| Typical Application |
Analogue/digital |
| Type of Power Supply |
DC |
Hazardous Area Specifications
| Parameter |
Value |
| Gas Groups |
IIC, IIB, IIA |
| Zones |
Zone 0, Zone 2 (ATEX/IECEx) |
| NEC Hazardous Rating |
Class I, Division 2; Class I, Zone 2 |
| Certification |
II (1) GD [Ex ia] IIC |
| ATEX Category |
II 1 GD |
| Ingress Protection |
IP20 |
Mechanical Specifications
| Parameter |
Value |
| Width |
12.6 mm |
| Height |
90 mm |
| Depth/Length |
105 mm |
| Weight |
140 g |
| Enclosure Material |
Polycarbonate |
| Mounting |
35 mm T-section DIN rail (EN 60715) |
| Terminals |
Removable screw terminals, colour-coded |
Environmental Specifications
| Parameter |
Value |
| Minimum Operating Temperature |
-20°C |
| Maximum Operating Temperature |
+60°C to +65°C |
| Degree of Protection |
IP20 |
Certifications & Approvals
| Certification |
Status |
Certificate Number |
Region |
| ATEX |
✅ Certified |
-- |
Europe |
| IECEx |
✅ Certified |
-- |
International |
| CSA |
✅ Current |
1345550 |
North America |
| FM (Factory Mutual) |
✅ Current |
FM16US0708X |
USA |
| KOSHA (Korea) |
✅ Current |
14-AV4BO-0341 |
South Korea |
| LR (Lloyd's Register) |
✅ Current |
LR2347021TA |
International/Marine |
| CCC Ex (China) |
Available |
-- |
China |
| EAC |
⚠️ Expired |
TC RU C-GB.ME92.B.00739 |
Russia |
| RoHS |
✅ Compliant |
-- |
-- |
Function Description
The MTL7728+ 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.
How it works:
- Voltage limiting: Zener or forward-connected diodes clamp the output voltage to a safe level (28V) if the safe-area voltage rises above normal operating levels
- Current limiting: A series resistor (300Ω) limits fault current to a safe value (93mA)
- Fusing: A fuse protects the diodes, and the two stages of voltage limitation ensure continued safety if either stage should fail
- 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
Applications
The MTL7728+ is specifically designed for general-purpose I/O protection in hazardous area installations:
| Industry |
Application |
| Oil & Gas |
Solenoid valve control and proximity sensor monitoring on offshore platforms and refineries |
| Chemical Processing |
Controller output protection and switch input isolation in IIC classified areas |
| Pharmaceutical |
Digital I/O protection for batch processing equipment requiring Ex ia IIC certification |
| Factory Automation |
Proximity detector interfacing and solenoid control in hazardous locations |
| Power Generation |
Turbine control systems with analogue/digital I/O in hydrogen-containing environments |
| Fire Detection |
Conventional fire detection systems for protection within hazardous areas |
| Marine & Offshore |
Marine control systems requiring LR marine certification |
Typical field devices connected:
- Solenoid valves (low-power)
- Proximity detectors (NAMUR)
- Switch inputs (limit switches, pressure switches)
- 2-wire transmitters (with bussed power)
- Analogue I/O circuits
- Conventional fire detectors
Installation Information
| 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 |
Important Installation Notes:
- 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 for MTL728+
- Secondary fuses can be latched in a disconnect position to break circuits during commissioning and maintenance
Ordering Information
| Item |
Details |
| Part Number |
MTL7728+ |
| Brand |
Eaton (Crouse-Hinds series MTL) |
| Product Family |
MTL7700 Range — Zener Barriers |
| Tariff Code |
85369095 |
| EAN |
3066227675743 |
| Weight |
0.140 kg |
| Country of Origin |
India |
| Condition |
New, Original, Factory Sealed |
| Minimum Order Quantity |
1 piece |
| Warranty |
Manufacturer's standard warranty |
| Shipping |
Immediate dispatch via DHL, FedEx, UPS, TNT |
Contact our sales team for volume pricing, datasheet downloads, or technical application support.
