DO Digital Output is the abbreviation of digital output. Its output has two states, on and off, just like the contact of a relay.
The abbreviation of AI analog input, analog signal input.
The abbreviation of AO Analog Output, the output of analog signal.
The above four signals are generally a module, so the corresponding module is called XX module, and there are also digital quantity mixing module and analog quantity mixing module, such as digital quantity input/output module, which means that this module has digital quantity input, output and analog quantity similarity.
These modules transmit the corresponding signals to the CPU of PLC after conversion, so that the CPU can know the state or data of the corresponding channel.
DCS is different from PLC, which is developed on the basis of electrical relay control, DCS is developed from field instrument control, and DCS is loop control, which is different from PLC sequence control. But now they are infiltrating each other. Each has some functions.