Z-System – Zener Barriers
Product Specifications
20
16-
03
11
Figure 2.5
Total current drains through the zener diodes
If the Zener Barriers are provided with a resistor, this limits the short circuit current
to a safe value in the event of a short circuit of the connecting wiring in the
hazardous area or a connection to earth of the wiring attached to terminal 1.
Some barriers are available with a resistor connected between the output
terminals. These are used in 4 mA to 20 mA transmitter circuits. The resistor
converts the current in the intrinsically safe circuit into a voltage that can be
measured in the non-hazardous area.
Fuchs zener barriers can be used in many applications. In the simplest
case, a 1-channel zener barrier with a ground connection is used. But in many
applications it is not desirable that the intrinsically safe circuit is connected
directly to ground. If the circuit in the non-hazardous area is grounded, under
some circumstances grounding of the intrinsically safe circuit can lead to faults
within the system. In this case, quasi-ground-free intrinsically safe circuits can be
constructed with 2-channel or multi-channel zener barriers. Fuchs offers
2- and 3-channel zener barriers in the same housing as the 1-channel zener
barriers.
Double grounding of intrinsically safe circuits is not permitted. The insulation
voltage of the wiring and field devices, measured with respect to ground, must be
greater than 500 V AC.
Zone 0, 1, 2
Div. 1, 2
(+)
(-)
50 mA
24 V
Power
supply
Load
> 25.5 V