I/O module's test signal terminals

unsaint32 · May 17, 2014

Some safety relay I/O modules have test signal generators. For example, Sick Safety Controller's I/O module has two safety signal generaros, X1 & X2. Many I/O modules have these test signals. What are these test signals? Can someone describe some applications that can explain why it is called "test" signal? Thanks.

LadderLogic · May 18, 2014

These are outputs that switch on and off at certain frequency. When a safety device, like an E-Stop button contact, is connected between such a "test" terminal and a "safe" input, the safety controller expects to read the same pulse pattern back. This indicates the integrity of the safety circuit and adds a degree of reliability as compared to a circuit where e-stop is wired just to a DC power bus.

unsaint32 · May 18, 2014

LadderLogic said:
These are outputs that switch on and off at certain frequency. When a safety device, like an E-Stop button contact, is connected between such a "test" terminal and a "safe" input, the safety controller expects to read the same pulse pattern back. This indicates the integrity of the safety circuit and adds a degree of reliability as compared to a circuit where e-stop is wired just to a DC power bus.

I see, it's sort of like the flashing LED for network Link status. Makes sense. Thanks Ladderlogic.

I/O module's test signal terminals

unsaint32

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LadderLogic

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unsaint32

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