PLC / SCADA standard structures / data types

I’m just starting programming on a rather large process control system (compared to what I’ve been working on before). I therefore feel the need to establish some good standard UDTs for the motors / valves etc.

Does anybody have good examples of the data structures you are using?
I need to build:

  • Automatic valve (feedback in both directions).
  • Automatic valve (feedback only in open position).
  • Automatic valve (no feedback).
  • Motor with stepless speed control and PID control (with bus controlled VFD).

What i/o do you have for the Automatic Valve with no feedback?

I like to start with the most basic device and creating a udt for that and then embed that udt in other udt’s that have more signals, or is an assembly of devices.



_Run _HOA _Fail _Pump udt _VFD Speed _Manual Speed _VFD udt _Valve udt _Flow Meter udt

As far as specifics… That is why you are the integrator, you have the tools to design a udt that will work best for your application.

Hi Zack,

I have found an open publication for a object structure that I’ve utilized in this project (industrial wastewater filtering / fat flotation and clorine desinfection).
The structure i have used is UNICOS (UNified Industrial COntrol System) developed by the CERN-team.

Although it uses quite large data structures, i have found it to be extremely flexible.
What i find smartest about it is that the structure contains a “parameter” object.

These parameters are for example:
-On/Open feedback present?
-Off/Closed feedback present?
-Local drive allowed?
-Fail safe position open?

Of course these parameters can also be utilized in the SCADA system, which means that i can differentiate the UDT for a valve depending on if the valve has feedback sensors or not.

With only two objects; “Analog” and “ONOFF” i can control all my components; valves (on/off or control), pumps (contactor or VFD driven) etc.

The standard is located here: … bjects.pdf