How to interface external length counter in PLC program

[mahathir]

Good day to all,

Right now, i try make improvement to add one external length counter to my machine. I want when the machine running in Manual mode and until 20m length,
the buzzer or alarm will trigger. But i don't know how to write the ladder diagram
and relate it with the external length counter.

Hope somebody can help.

Thanks

 

[allentcm]

How do your length counter interface with your PLC, via digital pulse?