1756-RM001B-EN-P, Using ControlLogix in SIL2 ... - Tuv-fs.com

Faults in the ControlLogix System 7-3Examining an Analog InputModule’s High AlarmControlLogix analog modules perform processing and comparison offield data values right on the module, allowing for easy examinationof status bits to initiate a fault.For example, the 1756-IF8 module can be configured withuser-defined alarm values that, when exceeded, will set a status bit onthe module which is then sent back to the controller. The user maythen examine the state of these bits to initiate a fault as shown inFigure 7.2:Figure 7.2Ch1HAlarmFaultFaultAlarm to OperatorIn the example above, the High Alarm bit for channel 1 (CH1HAlarm)is being examined for an On condition to initiate a fault. Duringoperation, as the analog input module processes analog signals fromthe field sensors, if the value for channel 1 exceeds the user-definedvalue configured for Channel 1’s High Alarm, the (CH1HAlarm) bit isset and sent to the controller and a fault is declared.Publication 1756-RM001B-EN-P - October 2003