Z-System – Zener Barriers
Product Specifications
20
16-
03
9
On the control side (1) typically control circuits are connected in non-hazardous
area. The condition that the control circuit must satisfy, is that it must not contain a
source whose potential relative to earth is greater than 250 V AC or 250 V DC.
On the field side (2) field devices are connected in hazardous area. The field
devices are intrinsically safe apparatus and must be certificated unless the
electrical values do not exceed any of the following values:
• Voltage 1.5 V
• Current 0.1 A
• Power 25 mW
Fuchs zener barriers are identified in terms of:
• Voltage, i. e. 10 V
• Resistance. i. e. 50
• Polarity, i. e. positive polarity
These figures correspond to the zener voltage U
z
and the total resistance of all
zener barrier components. The figures represent the safety values. The values
stated on the nameplate correspond to the "worst case" data for U
z
(U
o
, V
oc
) and
I
k
(I
o
, I
sc
) determined during certification.
I
k
is obtained by dividing U
z
by the resistance R.
Ideally, zener diodes would not allow any current in the reverse direction until the
zener voltage U
z
has been attained. In practice, zener diodes do allow a small
leakage current, the value of which increases as the applied voltage is increased.
The operating range of a zener barrier must therefore be such that it is below the
zener voltage, so that the leakage current is restricted to a minimum. Zener
barriers are normally tested to ensure that at the prescribed voltage the leakage
current is smaller than 10
µ
A.
Note!
These values do not correspond to the operating range of the zener barrier.