Ossd Safety Outputs; Important Note Concerning Ossd Safety Outputs; Ossd - Reer MZERO Installation, Use And Maintenance Manual

OSSD SAFETY OUTPUTS

IMPORTANT NOTE CONCERNING OSSD SAFETY OUTPUTS

➔
OSSD safety outputs are periodically tested against possible stucks to 0V or +24VDC or
against bad cabling (e.g. two OSSD outputs shorted together). The test method chosen to
perform this safety check is the "voltage dip" test: periodically (every 120 ms) and for a very
short time (< 120 µs) each OSSD output is forced to 0VDC and if the test results are not
consistent the system goes in fail and into a safe state.

OSSD

MZERO is equipped with OSSD (static semiconductor safety outputs) dual channel.
These outputs are short circuit protected, cross circuit monitored and supply:
• In the ON condition: (Uv-1,2V)...Uv (Uv = 24VDC ± 20%)
• In the OFF condition: 0V...2V r.m.s.
The maximum load is 400mA@24V and corresponds to a minimum resistive load of 60.
The maximum capacitive load is 0.68 F. The maximum inductive load is 2 mH.
➔
External devices cannot be connected to the outputs unless explicitly planned in the MZD
program configuration project.

Common cause failures between OSSD outputs must be excluded by observing an
appropriate cable installation (i.e. separate cable paths).

In conditions of active outputs the module provides on both outputs a voltage equal to 24V
referred to 0VDC.
The load must therefore be connected between the output terminals and 0VDC.
8541403 • 19/07/2021 • Rev.1
STAND ALONE PROGRAMMABLE SAFETY CONTROLLER
Figure 6 – Voltage dip test
Figure 7 – OSSD correct wiring
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