PLC and DAQ

About decade ago I totally switch to DAQ due to cost of the whole system. Since PLC by itself to add a Human Machine Interface by then you need a touch screen which is quite expensive especially a color one, it event more expensive compare to PLC and its IO modules all together. Moreover it work relatively slow compare to PC base solution, as CPU cycle time is depend on how big your ladder program is. On another hand for each specific application where a motion control is needed you must add a motion control module which is far from perfect at that time. If you need a temp control you would add another module and so on. But with PC base you have almost everything in one board. The flexibility is only depend on your programming skill and you don't need an expensive HMI touch screen as MS Visual Studio give you a freestyle graphical programming whereas on a touch screen you can use only the library offer and hard to customize to what you need (special one).

The good of PLC is it work in a hazard environment and robust. We have Omron CQM1 for DI water plant, after a big flooding in Thailand ( stay under water for more than 2 months) after we clean dry and bake ( remove every single board into basket) and re-assembly it back and upload a backup ladder program, it work wonderfully.