PLC programming issue: detecting pulses
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There is now a device for detecting shaft overspeed alarms. Pulses are sent to the DI module of the S7300 (with an input delay of up to 4.8 ms); under normal conditions, it receives signals with a pulse width of 30 ms and a period of 1 second. In the event of a fault, the pulse frequency increases, and both the pulse width and the period change accordingly, eventually reaching a pulse width of 5 ms and a period of 160 ms. How can an alarm be triggered in case of a fault through programming? Just outline the approach – what instructions are needed? Also, is it necessary to enable the system’s pulse capture function, and should the filtering time be reduced?
Is your 300 DI module connected to the 300 CPU or the 400 CPU? You need to consider the program execution time; with ob1, it isn’t necessarily less than 5ms every time (it depends on how your program performs)