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4 Safety Function Blocks
NX-series Safety Control Unit Instructions Reference Manual (Z931)
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SF_TestableSafetySensor
• You can use this FB to execute a test for a type-2 ESPE sensor that has an external test function.
• The test simulates the operation of the sensing device and detects potentially hazardous problems
(e.g., loss of sensing unit detection ability and response times that exceed specified values).
• During the test, the FB holds the safety output (S_OSSD_Out), so the test can be performed without
stopping the safety output to the actuator.
• The FB simulates an entry into the hazardous area of a safety sensor that has an external test func-
tion (e.g., type-2 ESPE), and monitors the operation and the maximum response time.
• It is assumed that an external safety-related control system (e.g., machine) starts a periodic test. An
ESPE must be connected to an applicable input device (e.g., safety input terminal).
• You must select the ESPE according to the required category in product specifications IEC 61496-1,
IEC 61496-2, IEC 61496-3, and IEC 13849.
• You must monitor testing with a separate mechanism to ensure that the test is started at a suitable
interval.
• Activate the S_StartReset and S_AutoReset inputs only when you can ensure that no hazardous
state will occur as the result of starting the Safety CPU Unit.
Test Mode
1. When the StartTest input changes to TRUE, the S_TestOut output is set to FALSE and the inter-
nal monitor is started.
2. The S_TestOut signal stops light emission. (Monitoring for the first TestTime starts.)
3. S_OSSD_In changes to FALSE. (Monitoring for the second TestTime starts.)
4. S_TestOut changes to TRUE.
5. Light emission from the emitter starts.
6. The S_OSSD_In sensor input changes to TRUE.
7. The monitoring time is stopped.
8. S_OSSD_Out is set to TRUE during the test.
Startup Control Options
• Control starts after the FB is activated.
• Control starts after a protective device interrupt.
Function
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