S_GuardSwitch1 and S_GuardSwitch2 inputs

State-controlled inputs for the connected position switches of the door. For the S_GuardMonitoring output to switch to SAFETRUE, both inputs S_GuardSwitch1 and S_GuardSwitch2 must switch to SAFETRUE within the time set at DiscrepancyTime.

Data type: SAFEBOOL

Initial value: SAFEFALSE

Connection: Connect these inputs either directly or via other safety-related functions/function blocks to the switches of the safety equipment connected to the Safety Logic Controller (for example, a door or a separate, possibly positively-driven, single-channel or two-channel position switch). Constant SAFETRUE or SAFEFALSE values are not permitted.

NOTE:

If only one signal reports the status of the door (one position switch only), this must be connected in parallel to both inputs S_GuardSwitch1 and S_GuardSwitch2. In this case, a time of 0 seconds must be set at DiscrepancyTime.

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

Value	Description
SAFETRUE	Position switch reports the closed state of the safety equipment. To ensure that the S_GuardMonitoring output becomes SAFETRUE, both inputs S_GuardSwitch1 and S_GuardSwitch2 must report the closed state of the safety equipment within the time set at DiscrepancyTime (S_GuardSwitch1 and S_GuardSwitch2 switch to SAFETRUE). If no start-up/restart inhibit has been specified for the function block, the status at the inputs S_GuardSwitch1 and S_GuardSwitch2 can cause the S_GuardMonitoring output to immediately switch to SAFETRUE. Refer to the hazard message below this table.
SAFEFALSE	Position switch reports the open state of the safety equipment.

Value

Description

SAFETRUE

Position switch reports the closed state of the safety equipment. To ensure that the S_GuardMonitoring output becomes SAFETRUE, both inputs S_GuardSwitch1 and S_GuardSwitch2 must report the closed state of the safety equipment within the time set at DiscrepancyTime (S_GuardSwitch1 and S_GuardSwitch2 switch to SAFETRUE).

If no start-up/restart inhibit has been specified for the function block, the status at the inputs S_GuardSwitch1 and S_GuardSwitch2 can cause the S_GuardMonitoring output to immediately switch to SAFETRUE.

Refer to the hazard message below this table.

SAFEFALSE

Position switch reports the open state of the safety equipment.

WARNING
	UNINTENDED START-UP Be sure that your risk analysis includes an evaluation for the state change at the S_GuardMonitoring output after applying the SAFETRUE status to the S_GuardSwitch1/S_GuardSwitch2 input. Make certain that appropriate procedures and measures (according to applicable sector standards) have been taken to help avoid hazardous situations when applying the SAFETRUE status to the S_GuardSwitch1/S_GuardSwitch2 input. Use appropriate safety interlocks where personnel and/or equipment hazards exist. Failure to follow these instructions can result in death, serious injury, or equipment damage.

WARNING

UNINTENDED START-UP

Be sure that your risk analysis includes an evaluation for the state change at the S_GuardMonitoring output after applying the SAFETRUE status to the S_GuardSwitch1/S_GuardSwitch2 input.
Make certain that appropriate procedures and measures (according to applicable sector standards) have been taken to help avoid hazardous situations when applying the SAFETRUE status to the S_GuardSwitch1/S_GuardSwitch2 input.
Use appropriate safety interlocks where personnel and/or equipment hazards exist.

Failure to follow these instructions can result in death, serious injury, or equipment damage.

NOTE:

Different (asymmetric) states at inputs S_GuardSwitch1 and S_GuardSwitch2 after the time set at DiscrepancyTime has elapsed only produce an error message during the closing operation and the S_GuardMonitoring output remains SAFEFALSE.

Single-channel or two-channel position switch?

Irrespective of whether there is a single-channel or two-channel connection between the position switch involved and the Safety Logic Controller, both inputs S_GuardSwitch1 and S_GuardSwitch2 are only connected to one signal each.

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

Both of these scenarios are outlined in the Overview for this function block and the Application examples.

One or two position switches?

If you are setting up safety equipment with one position switch, this involves connecting the signal from this switch to input S_GuardSwitch1 and drawing a graphical connecting line to the second input S_GuardSwitch2. Both inputs are then controlled by the same signal from the safety-related input device, which is connected to the safety equipment switch.

If you are using two position switches and, as a result, two signals, connect one signal to input S_GuardSwitch1 and the other one to S_GuardSwitch2.

Both of these scenarios are outlined in the Overview for this function block and the Application examples.