Hello,

Is there a suggested limit to the number of I/O points that PLC/PAC can use? Is there an I/O count where it would be better to use a DCS instead?

Thanks,
rhoadesk

 

Please understand that a DCS is a SYSTEM consisting of HMI, network (data hiway), and multiple controllers. The controllers may contain their own I/O, or they may use remote or fieldbus I/O. A PLC/PAC is a single controller that may contain both integral and/or remote I/O. Networks of PAC/PLC may exist and methods of sharing data may also exist, but you (or your system integrator) will be responsible to install the software to make such networks of PAC/PLC actually work. The DCS integrates all network components because the DCS supplier has done the integration to the limit of the network capacity for which they have tested.

Dick Caro
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Richard H. Caro, Certified Automation Professional, CEO, CMC Associates,
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