RADWAG PUE HX5.EX, Руководство пользователя

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9.8.2. Passive Inputs in Ex Zone
Configuration intended to be used in hazardous area. External buttons (relay
contacts) are powered using an external power supply.
The external power supply must be an intrinsically safe device characterized
with features corresponding to the existing explosive atmosphere.
It is forbidden to connect electric potential and ground of
internal power supply unit (Uo and GND on IN/OUT interfaces
terminals of the indicator) with an external intrinsically safe
power supply. This would result with loss of intrinsic safety.
All instruments connected to indicator’s digital IN/OUT
require ‘ia’ or ‘ib’ protection.
9.8.3. Passive Inputs Outside Ex Zone
Configuration intended to be used outside hazardous area. External buttons
(relay contacts) are powered using an external power supply placed outside the
hazardous area.
The power supply and the external buttons (relay contacts) are connected via
relevant diode barriers.