MTL Barries - MTL7788+ - ANALOGUE INPUTS (HIGH LEVEL)

The MTL7788+ is a shunt-diode intrinsically safe (IS) barrier that limits energy to a hazardous area by using zener diodes and resistors to clamp voltage and current. It separates the safe and hazardous areas, preventing high-energy faults in the safe area from igniting the hazardous environment. The barrier also provides an IS earth connection via a DIN rail mount and has removable terminals for easy installation and maintenance

Working principle

• Energy limitation: The device contains a network of zener diodes and resistors that act as a protective "shunt." This network is designed to limit the voltage and current that can pass from the safe-area to the hazardous-area circuits.
• Voltage and current clamping: If a fault occurs in the safe area (e.g., a short circuit), the zener diodes will conduct, clamping the voltage to a safe level and diverting excess current to the IS earth connection. This prevents the energy from reaching the hazardous area, which could cause an explosion.
• Isolation: The barrier provides a physical and electrical separation between the circuits in the hazardous and safe areas.
• Intrinsically safe (IS) earth connection: The barrier is mounted on a DIN rail, which provides a direct, low-resistance earth connection for the IS circuit.
• Removable terminals: For easy installation and maintenance, the terminals are removable. You can simply unplug the terminal block from the side of the barrier to disconnect the loop.
• Polarity: The MTL7788+ is a non-polarized barrier, meaning it can be installed without regard to the polarity of the incoming signal. A grey label indicates this.

The MTL7788+ is a shunt-diode safety barrier that operates on the principle of intrinsic safety. Its primary function is to restrict the transfer of electrical energy from a non-hazardous (safe) area to a hazardous area, thereby preventing the ignition of an explosive atmosphere.

ANALOGUE INPUTS (HIGH LEVEL)

Working Principle

The core principle involves limiting the voltage and current that can enter the hazardous area under both normal and fault conditions. This is achieved using a combination of Zener diodes, resistors, and a fuse:

• Zener Diodes: These are connected between the signal lines and an integral safety earth connection. If the voltage on the signal lines from the safe area exceeds a specific safe threshold, the Zener diodes conduct, diverting the excess voltage and current safely to the earth.
• Resistors: A series resistor limits the current that can flow into the hazardous area, even if the safe-area voltage is at its maximum.
• Fuse: An internal fuse is used to protect the Zener diodes and the circuit. If a major fault occurs that causes a significant current flow, the fuse blows, permanently breaking the circuit and ensuring safety.

Function and Application

 Full Datasheet