Hello.

We have recently worked on a cascade controller using Siemens S7 1214C AC/DC RLY with an SM1234 AI/AQ module. After encountering many problems using 234-4HE30-0XB0, so we decided to upgrade to 234-4HE32-0XB0 (basically because you've the option to change the inputs and ouputs to 4-20mA without scaling).

However, we have a problem with the output "%QW96". When we put  "%DB4" in manual and change the output to 0%, the valve shows about 25% and we measure 8mA.

When we change the output to 50% we measure 15mA (69%), and when we manually send 100% we measure 20mA.

Basically our problem is that the actual analog output doesn't match up with the PID-output on TIA-portal. This problem occured on both modules.

In attachment are some screenshots from our program, and wiring diagram.

Thanks

Hi,

When you use Output PER, you must be careful because in the configuration of PID you can scale the output and may be there is an error specific in the limits of the scaling, if you want you can use Output in the block PID and you must use NormX and Scale X for get the correct value

Regards