Touch screen is a human-machine interface, but touch screen is only one kind of human-machine interface. The HMI also includes non-touch screen, and the upper computer, text display, etc. Connecting PLC is always a function of HMI, and the operator interface that can realize human-machine interaction is HMI.
The human-machine interface is a platform for a person to operate a PLC. The platform provides a program-human interface, a medium for the transmission and exchange of information and a dialogue interface between humans and computers, and is an important part of the computer system. It achieves the conversion between the internal form of information and human can accept the form, where involved in the field of human-computer information exchange there is a human-machine interface.
Touch screen is a PLC human-machine interface, people can adjust parameters or monitor parameters by touching the buttons on the screen, etc.. But the human-machine interface is not necessarily all touch screen, there are a number of buttons installed on the operating panel, people through the button to monitor the PLC operation. The screen of this interface is only used to observe the parameters, no touch operation function.
Touch screen is a human-machine interface, but touch screen is only one kind of human-machine interface. The HMI also includes non-touch screen, and the upper computer, text display, etc. Connection to PLC is always a function of the human-machine interface, the operator interface that can achieve human-computer interaction is the human-machine interface.
Strictly speaking, "touch screen" is an input device with touch operation function of the HMI, in the factory with touch input function of the HMI is customarily called "touch screen".