ABB FSO-12, User Manual

Page: 29 / 388

Safety information and considerations 29
If an FSO I/O or a safety fieldbus failure occurs, the FSO module activates the SSE
function (or the STO function, if an STO request is connected to the I/O). In other
internal failure situations, the FSO module activates the STO function. Depending on
parameter settings, the SSE function can be similar to the STO function (when
configured as “Immediate STO”, for more information see section
Configuring SSE on
page 248 ).

I/O
The FSO module supports input and output redundancy.
The FSO module provides an option for applying diagnostic pulsing for its inputs and
outputs. When applied, the pulsing enables the FSO diagnostics to detect cable
failures as follows:
• Inputs : Open-circuiting and short-circuiting failures are detected with diagnostic
pulsing. The failures that short-circuit the sensor are detected upon input
activation when redundant connection is used.
Note : If only one of the redundant inputs is activated upon a safety function
request, the FSO module activates the safety function but it cannot be
acknowledged before the failure has been repaired.
To acknowledge the safety
function, you must set both input channels down and up at the same time or,
switch the power off and on.
Note: ABB recommends to use external devices which are equipped with either a
positive mechanical action or force guided contacts.
Note: With external test pulses, the length of the pulses shall be 0,5 - 2 ms. Test
pulses must be in totally different phasing, and must not overlap.
• Outputs : If diagnostic pulsing is used, failures that short-circuit the signal to the
voltage supply or the ground potential are detected. Failures that open-circuit the
actuator are not detected.
You can select the logical signal level for each digital output by a parameter. The
selections are Active low (0 V) and Active high (24 V). Select the level depending on
1. Failure is detected
2. Failure is detected upon
input activation when
redundancy is used
TP2
DI1
DI2
TP1
Diagnostic pulse 2
Diagnostic pulse 1
Digital input 1
Digital input 2
1
1
2
1