517.001.301FC MTL7728+ Zener Safety Barrier for Conventional Detection Circuits

The MTL7728+ is an intrinsically safe, zone-powered, Zener-diode barrier for use in conventional fire detection systems for protection within hazardous areas.

Each Zone contains two stages of pulse-tested Zener or forward- connected diodes and an ‘infallible’ terminating resistor. In the event of an electrical fault in the safe area, the diodes limit the voltage that can reach the hazardous area and the resistor limits the current. 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 are employed.

Model MTL7728+ is certified ‘ia’ for all zones and ‘IIC’ for all explosive atmospheres.

The MTL7700 Series intrinsically safe shunt-diode safety barriers are innovative devices designed to provide exceptionally high packing densities, straightforward installation and simplified connection, commissioning and maintenance facilities. The MTL7700 Series include secondary replaceable fuses. These are useful where there is the possibility of faults occurring during commissioning, which would otherwise blow the barriers’ internal safety fuses.

One secondary replaceable fuse for each barrier channel is provided and is lower in value than the safety related fuse. Fuses are packaged in small mouldings which can be latched in a disconnect position to break the safe and hazardous areas during commissioning, maintenance and fault finding, thus avoiding the need for additional disconnect terminals.

Key Features

• Removable, colour-coded terminals
• Bussed power feed to other modules
• Relay and solid state switch modules
• Dual channel variants - 6.3mm per channel
• Proximity detector inputs
• Compatible terminal numbering and safety descriptions
• Dimensions: 105 x 90 x 12.6mm
• Number of Channels: 1
• Supply Voltage: 28 V dc
• Safety Voltage Maximum: 26 V dc
• Safety Current Resistance: 300ohm
• Safety Current Maximum: 93mA
• Signal Type: Analogue
• Minimum Operating Temperature: -20°C
• Maximum Operating Temperature: +65°C
• Hazardous Area Certification: ATEX
• Operating Temperature Range: Maximum of +65 °C