Details of the application example

This section describes a possible application in which the function block can be used to evaluate signal equivalence.

The function block must only be used in an actual application once a risk analysis has been conducted.

Details of the risk category/SIL/PL have not been included here, as classification is always based on the application in which the function block is used.

NOTE:

The use of the function block alone is not sufficient to execute the safety-related function according to the Cat./SIL/PL determined by the risk analysis. In conjunction with the safety-related I/O device used, additional measures must be taken to meet the requirements of the safety-related function. These include, for example, the appropriate wiring and parameterization of the inputs and outputs as well as measures to exclude (design out) errors that cannot be detected. For additional information, refer to the documentation provided with the safety-related I/O device used.

NOTE:

Refer to the notes in the User Manual on proper electrical connection of the Safety Logic Controller and all extension modules (e.g., connecting the two-channel sensor or switch).

Evaluating signals for an emergency-stop control device with two N/C contacts

This example illustrates two-channel control of the safety-related SF_EmergencyStop function block with the help of the safety-related SF_Equivalent function block.

The emergency-stop control device is connected to the inputs I0 and I1 of the safety-related input device SDI with an ID of 1 in accordance with the closed-circuit current principle (two N/C contacts). The two N/C contacts are fed to the S_ChannelA and S_ChannelB inputs of the safety-related SF_Equivalent function block for evaluation purposes.

The S_EquivalentOut enable signal of the SF_Equivalent function block resulting from this is connected to the S_EStopIn input of the SF_EmergencyStop function block for further evaluation. The S_EquivalentOut output of the SF_Equivalent function block is SAFETRUE if both S_ChannelA and S_ChannelB inputs switch to SAFETRUE at the same time (emergency-stop control device is not actuated) and the SF_Equivalent function block does not report any errors as regards exceeding the time set at DiscrepancyTime.

A start-up inhibit after the Safety Logic Controller has been started up or after the function block has been activated and a restart inhibit after the emergency-stop control device has been unlocked is set for the SF_EmergencyStop function block. Both inhibits are removed by pressing the reset button connected to input NI0 of the standard input device DI with an ID of 1.

NOTE:

The enable output S_EStopOut of the SF_EmergencyStop function block is directly connected to a global I/O variable or to an output terminal of the application via additional safety-related functions/function blocks.

Connect the S_EStopOut enable output of the SF_EmergencyStop function block to the S_OutControl input of the SF_EDM function block, for example, thus implementing a two-channel output connection.

Further Information

For more detailed information, refer to the description of the corresponding safety-related function block.

S1	Emergency-stop
S2	Reset
	See note above the illustration.