The IT world is full of acronyms, from programming languages like BASIC and SQL to terms like RAM and ROM. If you have ever sat in front of a computer, you may have been part of an HMI, or human machine interface.
HMI might seem like a fancy term, but the definition is actually quite simple. The term HMI refers to the interface between the operator and the controller. In its simplest terms, the HMI is the controller operating panel. That panel typically includes a numeric keypad and an LCD screen designed to display text as it is entered.
With an HMI system, the human operator uses the numeric keypad to input data into the application. The nature of the data will differ from one application to the next, but if a keypad is used to enter data the system is considered an HMI.
The HMI display can be used to display messages for the operator, sending alerts when data is entered incorrectly or when further information is required. If, for instance, the keypad is used to input date and time information, the screen can display an error message if an invalid time or date value is entered. This helps ensure the accuracy of the entered data, reduces the need for back-end auditing and keeps operators on their toes.
The display screen can also be used to display variable information from the program, showing a different screen depending on the data entered by the operator. If the operator enters an affirmative answer to a particular question, the display screen can pop up a new question requesting further information. If the original input is negative, the system skips to the next question instead.
Back-end processes are in place to make the magic happen. The operator does not need to be aware of these processes; in fact most human operators will not even think about them. The important part is that they are in place and that they pop up the right screens and display the proper messages in response to user input.
The display editor is used to create HMI messages, while the aptly-named variable editor creates the variable information fields. HMI applications are used in a number of applications, including the fields that contain user names and passwords.
Keypad-based systems are among the most common human machine interfaces, but they are by no means the only ones. There are many different kinds of HMI, and you probably interact with a number of them in your daily life.
When you pass one of those electronic billboards on the highway, you are interacting with an HMI. That particular HMI is designed to give you vital information on traffic conditions, accidents and construction zones. Businesses also use LED signs to tell customers about sales, communicate their hours and share information. That also is a form of HMI.
The industrial monitors used in factories, power plants and manufacturing facilities are another form of HMI. These monitors provide vital information to the human operators, passing on computer-generated data and notifying the staff whenever predetermined parameters are exceeded.
A growing form of HMI is the touch screen. While touch screens were once quite rare, the incredible popularity of the iPhone and other smartphones has catapulted them to the mainstream. Touch screens make it easy for the human holding a smartphone or tablet to type messages, change the size of screen text and move between screens.
No matter what the specific design, HMI displays allow computers and people to talk to one another. Whether you are typing on your smartphone screen, entering data at your job or driving down the highway, you are interacting with an HMI.