When PLC inputs the input signal changes PLC output reacts to the input changes will take some time, a phenomenon called the PLC input/output response lag.
From the above analysis, scanning cycle length depends on the length of the program. Scan cycle is longer, respond more slowly. As each scan cycle is only one I/O refresh, each scan cycle PLC input and output status register is updated, so the system input and output hysteresis, which to a certain extent, reduce the response speed of the system. Industrial field interference is often, shorter hours in pulses, PLC input/output response lags, the General requirements of industrial control, is perfectly allowed, can also serve to enhance the anti-jamming ability.
However, strict time requirements for control, fast response speed of the system, it is necessary to take measures to reduce the adverse effect of the input/output delay.