I would rather use siemens PLC S7-200 for this case, because of my own experience for about 4 years. For a small plant, I recommends you to make the routines with, serial comm from siemens as TX, and LabView as RX. One of my engineer are now research to build wider range of transmissions.
If you got something from your test, please contact me, then I'll use it to develop.
