S_GuardMonitoring input

State-controlled input for monitoring safety equipment.

Data type: SAFEBOOL
Initial value: SAFEFALSE

This input processes the status of the safety equipment (door open/closed). The signal present must be SAFETRUE so that the S_GuardLocked output can be switched to SAFETRUE (taking the other input signals into account).

Connection: Connect this input to a switch connected to the Safety PLC (e.g., door or a separate, possibly positively-driven, single-channel or two-channel position switch), either directly or via other safety-related functions/function blocks.

If the function block is activated (input Activate = TRUE), the possible values at this input lead to the following function block behavior:

Value Description

SAFETRUE The safety equipment is closed.
The S_GuardLocked output can be switched to SAFETRUE, provided that the other input signals show the corresponding values (Activate = TRUE, S_GuardLock = SAFETRUE, no start-up/restart inhibit specified by means of S_AutoReset and S_StartReset) and the function block has not detected any errors.
Refer to the warning below this table.

SAFEFALSE The safety equipment is open.
If SAFEFALSE is present at the S_GuardMonitoring input, the S_GuardLocked output is always SAFEFALSE, irrespective of all the other input signals.

Value	Description
SAFETRUE	The safety equipment is closed. The S_GuardLocked output can be switched to SAFETRUE, provided that the other input signals show the corresponding values (Activate = TRUE, S_GuardLock = SAFETRUE, no start-up/restart inhibit specified by means of S_AutoReset and S_StartReset) and the function block has not detected any errors. Refer to the warning below this table.
SAFEFALSE	The safety equipment is open. If SAFEFALSE is present at the S_GuardMonitoring input, the S_GuardLocked output is always SAFEFALSE, irrespective of all the other input signals.

If no start-up/restart inhibit has been specified for the function block, the SAFETRUE status at the S_GuardMonitoring input can cause the S_GuardLocked output to immediately switch to SAFETRUE.

WARNING

Unintended start-up

If no start-up/restart inhibit is specified:

Be sure that your risk analysis includes an evaluation for the state change at the S_GuardLocked output after applying the SAFETRUE status to the S_GuardMonitoring input.

Make certain that appropriate procedures and measures (according to applicable sector standards) have been established to help avoid hazardous situations when applying the SAFETRUE status to the S_GuardMonitoring input.

Use appropriate safety interlocks where personnel and/or equipment hazards exist.

Single-channel or two-channel position switch?

Irrespective of whether there is a single-channel or two-channel connection between the relevant position switch and the Safety PLC, the S_GuardMonitoring input is only connected to one signal.

If a two-channel position switch is used, either the input channels of the safety-related input device must be parameterized accordingly or the safety-related SF_Equivalent or SF_Antivalent function block must be connected upstream for evaluating or monitoring the two-channel signal (e.g., SF_Equivalent function block, if the position switch features two N/C contacts).

Note
Cross-circuit monitoring is not performed by the function block. It is your responsibility to perform this monitoring function outside of this function block in the safety-related control system.