How to Choose a Suitable HMI?
The Human Machine Interface (HMI) has a variety of hardware and software functions. The user should set the target application first, and then find a suitable solution according to the needs of the application. Look at the required HMI functions, and try to select the equipment and software that meet the needs. Most options are simple and straightforward, but some are not. So what details do we need to pay attention to when selecting a HMI?
Application environment
In the environment where conditions are available or easily wetted by water, the relevant protection of HMI should be done well. The installation must meet customer requirements, local installation regulations or preferences, and meet the requirements of certain levels or certification standards.
Product layout
Another thing to consider is whether to arrange the HMI indoors or outdoors. If it is outdoors, it will be affected by direct sunlight and heat damage to the components. Therefore, it is necessary to take measures to protect the outdoor HMI and place it in a cool area, or equipped with sunshade. The installation height of the monitor should meet the work requirements of employees, usually the distance from the ground to the monitor is about 66 inches.
Product specifications and characteristics
HMI contains sensitive display elements and backlights, and has higher requirements for the operating temperature range. The brightness of the display and the average backlight life should be carefully evaluated. Brightness represents the visibility of the display. The always-on backlight can indicate how long the device can be used.
Choosing the right display size usually requires to reach a balance. Larger displays provide users with more space to view data, develop graphics and so on. But a larger HMI costs more and takes up more space for control panel installation.
The user can compare the resolution in pixels, which determines the fineness of the graphic display. For some applications with special requirements, especially those involving data input, users may wish to use the onboard physical keypad or an external keyboard and mouse. Most designers follow the trend of the times and choose to use touch screens.
The difference between capacitive multi-touch and resistive touch screen is that the technology of former usually does not perceive gloved fingers and will be affected by water, but it does respond to multiple concurrent touches or gestures, and is usually suitable for consumer touch devices . On the other hand, industrial HMI usually uses resistive single-point touch technology. Resistive touch screens can respond to gloved fingers, only correctly respond to one touch at a time, and are not affected by external contaminants. It is usually the first choice for industrial applications.
Software configuration feasibility
Evaluate the configuration environment, runtime functions and remote access of HMI software: Programmers spend a lot of time in the HMI configuration environment. For users, it is important to obtain a software license and confirm whether the software is free. Typical users are interested in the ease of use of the software, functions such as drag-and-drop editing, single-click creation of objects, and whether the most commonly used objects are predefined.
The programmer wants to know whether the software has good support for input or output, whether it has database tools, whether it provides an effective copy method, and whether it contains a built-in simulation or test environment so that users can carry out proof of concept of the project and check the program without actual hardware. Programmers use configuration software to create tags that communicate with PLCs and other devices, to develop graphics linked to these tags, and to configure other built-in HMI functions.
If the user needs a specific appearance and function, it is better to briefly summarize and compare several types of HMI configurations, list the necessary functions, and obtain configuration software to test them.
Information visualization
Before choosing an advanced application, you may need to investigate the details of a specific HMI. Pay attention to the way which the HMI handles floating-point tags and any related math or calculations. The logic is usually executed inside the PLC; the information is displayed on the HMI. Some HMIs provide onboard logic, trigger evaluation, execution functions, and event manager functions. The above functions are helpful for more detailed display, and can participate in it as part of the machine logic. If complex functions are required, please pre-test each function.
Through the above detailed introduction, I believe that everyone has a clear direction for the choice of man-machine interface, so that you can choose a product that suits you.
