Rockwell Automation 440C Guardmaster 440C-CR30 Configurable Safety Relay User Manual - Manual (Page 130)

130 Rockwell Automation Publication 440C-UM001C-EN-P - November 2014
Appendix A Specifications
Test Pulse Evaluation
Integral test pulses are applied to the input circuit of safety sensor with
electromechanical outputs. The test pulse output signal becomes input signal of a
safety input through the contacts of the safety sensor. Sensors with electronic
OSSDe (output safety switching device electronic) semiconductor outputs have
their own test pulses and do not require a test pulse evaluation that is sourced by
the logic device.
Note: In case multiple input circuits are sourced by the same test pulse
output, a fault affects all inputs that are connected to this output.
Multi-Channel Signal Evaluation and Discrepancy Monitoring
Independent of the test pulse evaluation or sensor type, components can be wired
in a single, dual channel, or even three channel structure. In a dual or three
channel structure, all channels must be active to enable the SMF. Disabling at
least one of the channels will demand the safety function. These channels can be
monitored against discrepancy.
The discrepancy time is the amount of time that input channels of an SMF are
allowed to be in an inconsistent state before an instruction fault is generated. The
discrepancy time cannot be set in Single Channel Mode.
Sequence and Timing Faults
Typically applied to specialty safety functions such as Muting or Two-hand
control. It monitors the sequence of events to evaluate the validity of input
signals to enable the SMF.
Integral Test Pulses of Safety Outputs
Test pulses are applied to safety outputs to detect faults within the connected
periphery such as short circuits to 24V of 0V or cross-loop faults between two
output sources. Integral pulses on safety outputs are also used to help ensure the
safety integrity of the output itself, such as ability to switch off. An output fault,
internal or external, always requires a power cycle to test if the fault is recoverable
or not.
Note: To help ensure the ability to switch off actuator devices in case of
short circuits to 24V DC within the control line of one actuator, it is
recommended to use a pair of safety outputs controlling two redundant
switching actuators. Once the fault is detected, a second channel is able to
switch off the load. Fault exclusions of potential short circuits between
two conductors are also possible when following the requirements for fault
exclusions according to EN ISO 13849-2 Table D.3 and D.4, among
others protection (for example, cable conduit) and separated wiring of
safety signals.