How many maximum PID function blocks can be used for Unity Quantum CPU
There is no limit of the number of PID loops you can configure in the PLC. Only limitation will be the available pogram and data memory in PLC.
Once you run out of memory you won't be able to add more PID blocks. This PID block is also a type of the Function block that was available in PLC and the limitation of the same Function block will apply on this.