SSP North AB
30/08/2018
Manual V2f
22
3.1.3 Safety inputs
For details on programming safety inputs see chapter 13.11
Each input is a voltage input and both CPU: s read the
voltage level. Voltages above 80% of power supply voltage
are considered a logical 1, and voltages below 20% of
power supply voltage are considered a logical 0. Some
inputs can also be set to a specific voltage level (specified in
V).
When configuring inputs, an ON-state and an OFF-state
signal type must be specified. The allowed states you can
check in the matrix for recommended ON and OFF
selections (see chapter 13.11.2 Input signal types on page
ON and OFF states can be:
1. OV
2. VDC (= Supply voltage)
3. Any of the A, B, C and D pulse trains or inverted within the same
Safety Simplifier
4. E or inverted E-signal between Safety Simplifiers.
Warning!
Using a single input with 0V as the ON state signal (normally closed) as a safety
input violates the de-energisation principle, as a disconnected cable will result in the
input going to ON state. Always combine this type of input with a normally open input
to make sure a disconnected cable does not lead to ON state.
For ON and OFF state, we also recommend active signals
(coded pulsed signals) in both ON and OFF state (see matrix
for recommended combinations). Active signals give the
possibility to detect short circuits from external voltage.
Figure 3.2: SIL 3, PLe, CAT 4 redundant
input
Figure 3.3: SIL 3, PLe,
Cat 4 redundant input
