PID MultiI-Inputs, PROTRONIC PE Controller

I want to connect 5 inputs of temp. thermocouples sensors into the PID controller to perform the control process which is getting the average of the total five sensor readings and apply the control process then getting the output.

the controller is working for cascade control.

i want to know how to connect the 5 sensors to the controller and how to get the average value of them on it to make it the X value that the controller control it.

the manual is missing and i can`t find it on the internet also.
the device type is PROTRONIC PE Controller (ABB).

plz tell me what to do or if you don`t know that device cause it is pretty old, plz tell me how to solve this situation by drawing on any other similar type controllers.

thanks a lot.