Foxboro P0902XA FBM41 transmitter actuator

Description

Any PLC has self diagnosis function, and when the PLC is abnormal, its self diagnosis function should be fully utilized to analyze the cause of the fault. When there is an abnormality in the PLC, first check the power supply voltage, whether the screws and connectors of the PLC and I/O terminals are loose, and whether there are any other abnormalities. Then, based on the status of various LED indicators set on the basic unit of the PLC, check whether there are any abnormalities in the PLC itself and externally.

The following is an example of using the FX series PLC to illustrate the method of diagnosing the cause of PLC faults based on the status of LED indicators.

1. Power indicator ([POWER] LED indicator)
When supplying power to the PLC basic unit, the [POWER] LED indicator light set on the surface of the basic unit will light up. If the power is turned on but the [POWER] LED indicator light is not on, please confirm the power wiring. In addition, if the same power supply has drive sensors, please confirm whether there is a load short circuit or overcurrent. If it is not for the above reasons, it may be due to the inclusion of conductive foreign objects or other abnormal situations in the PLC, causing the fuse in the basic unit to blow. At this time, the problem can be solved by replacing the fuse.

2. Error indication ([EPROR] LED flashing)
When a program syntax error occurs (such as forgetting to set a timer or counter constant, etc.), or there is abnormal noise, conductive foreign objects mixed in and other reasons that cause changes in the content of the program memory, the [EPROR] LED will flash, the PLC is in the STOP state, and all outputs will turn OFF. In this case, the program should be checked for errors, as well as for the presence of conductive foreign objects and high-intensity noise sources.
When an error occurs, one of the values 8009, 8060, and 8068 is written to the special data register D8004. Assuming that the content written to D8004 is 8064, the error code can be determined by checking the content of D8064. The actual error content corresponding to the error code can be found in the error code table in the PLC user manual.