Safety system (SIL 2) solenoid (ASCO 327) is connected with SIS (Himax) through an I/P relay (Phoenix safety relay). The question is how will SIS know if solenoid has failed.
The diagnostic coverage of SIS will stop at I/P relay. As I know that Himax superimposes and AC over the DC to keep loop status in check. But this will stop at the relay (btw relay has its own hardwired DI health status feedback into SIS) and beyond that SIS has no visibility about loop health. Am i missing something, kindly guide how can SIS make sure that loop beyond relay is also healthy. Thanks
The diagnostic coverage of SIS will stop at I/P relay. As I know that Himax superimposes and AC over the DC to keep loop status in check. But this will stop at the relay (btw relay has its own hardwired DI health status feedback into SIS) and beyond that SIS has no visibility about loop health. Am i missing something, kindly guide how can SIS make sure that loop beyond relay is also healthy. Thanks