Hi

I'm trying to read the signal from an encoder with a freqency of 230Hz, which comes down to one pulse every 4ms. 

Will a SM521 HF module (6ES7521-1BH00-0AB0) be able to pick up the signal? I want to use this one because I can use the other inputs for sensors and it will keep the space used to a minimum opposed to using a seperate counter module.

Thanks in advance

hi,

no this is not the right module for your puroses. 

6ES7550-1AA00-0AB0 would be the rigth. This can up to 200kHz Input-frequency

hope this helps,

regards,

I have read that the HF module can cycle at 0.5ms, the downside of the counter module is that I will need a seperate DI. 

So the only solution would be the counter module?

The SM521 is only reading if your DI is true ore false. And you are detecting true or false only in program, so this is depending on your program cycle time. So if you have nearly the same signal frequency like the program-cycle-time, you are only detecting one state(true or false).

The counter-module counts every signal-change not depending on program-cycle-time. In program you are only reading the value, depending on what you need:

maybe ask a local Siemens distributer, what will be the best solution for your puposes.

hope this helps,

regards,