How to determine the number of analog or digital signal points for various components (valves, motors, etc.)?

It depends on the PID diagram; all signals related to the valve will be indicated there.

The main thing is to look at the PID diagrams, as different designers have distinct styles, and this also indirectly affects the investment costs. For example, parameters such as flow rate, pressure, level, and temperature usually correspond to one measurement point per AI node ； If a pneumatic control valve is designed with valve position feedback, there is one AI point and one AO point ； Pneumatic on/off valves usually have one DO point and two DI points ； Motors generally have three DI points for the on-site changeover switch, operation feedback, and thermal relay, as well as one DO point; however, in some designs, the power supply and the start/stop buttons of the on-site control panel are also connected to the control system as DI signals, and this depends on the designer’s decision. In short, use the conventional estimates for the quantities required, and leave a margin of about 25% for various models – that should be sufficient.

Sure enough, you gave me the answer I wanted. . . What about frequency conversion?

If the inverter is not connected to the control system via a communication interface, then typically there are frequency setpoints (AO), frequency feedback (AI), and fault signals (DI). Some designers also include signals related to the inverter’s power supply (DI) as well as local/remote control of the inverter (DI). You can determine which connections are necessary by referring to the inverter’s manual based on your own requirements.

This post was last edited by yame1996 on 2015-9-7 at 11:27. There are also feedbacks regarding current, overload, start/stop signals; more importantly, there are signals related to operation