Supervised Emergency stop example
The designer creates the following wiring for an Emergency stop digital input:
COM
300 Ω
100 Ω
Emergency
stop
When the Emergency stop is closed, the circuit has a resistance of around 75 Ω (the combined resistance of the 100 Ω
and 300 Ω resistors in parallel). When the Emergency stop is open, the circuit has a resistance of around 300 Ω.
The Emergency stop function requires that the digital input is normally activated. If the Emergency stop digital input is not
activated, the controller activates the Emergency stop alarm.
The designer therefore configures a customised function curve with an output of 0 up to 200 Ω, and an output of 1 above
200 Ω. The short circuit sensor failure is below 10 Ω. The wire break sensor failure is above 325 Ω.
DESIGNER'S HANDBOOK 4189340911K UK Page 420 of 521
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