Zener Barrier
The Zener barrier is a certified intrinsically safe interface. It is used to connect a certified intrinsically safe device located in a potentially explosive atmosphere (Hazardous area) to a non-certified device that is in a safe area.
The Zener barrier prevents the transfer of unacceptably high energy from the safe area into the hazardous area. Zener barrier properties are defined by the intrinsic safety parameters:
- Uo ... the highest open-circuit voltage at “HAZ” terminals
- Io … maximum current that can be taken from the "HAZ" terminals
The zener diode ZD limits the voltage that can reach the hazardous area in the event of a fault in the safe area (the fuse Po protects zener diode from being destroyed by a large current). The resistor Ro limits the current in the event of a fault in a hazardous area (Ro = Uo / Io).
The intrinsically safe device in hazardous area and the Zener barrier in safe area have to be comply. The intrinsically safe parameters Uo and Io of the Zener barrier must be less than the values Ui and Ii of the device (Ui and Ii are the maximum voltage and current values that can be applied to the device terminals according to the certificate).