A beginner’s guide to Human Machine Interface (HMI)

In the simplest of terms, any piece of hardware which helps in solidifying the interaction between humans and machines is referred to as Human Machine Interface or HMI. The purpose of such kind of interaction is for allowing the efficiency of operation and better control of machine manually while the machine simultaneously sends back information helping in the decision-making process of the operator.

HMI is the centralized controlling unit for the manufacturing lines for allowing convenient access to the system. HMIs usually work in coordination with Programmable Logic Controllers or PLCs. The PLCs are responsible for data input from sensors and its transformation into useful information into Boolean Algebra. This is further deciphered by HMI for making informed decisions.

Working of an HMI

For an HMI to work, first one needs components which are vital for designing a manufacturing control system. Secondly, one needs various sensors for input and output which are used for monitoring temperature, pressure, speed, feed rate and weight. After this, the next step is to select the PLC, which will receive all of this data and convert them into logical combinations.

A crucial aspect to a well-build HMI system is its software. The HMI is non-functional without pieces of codes written which help in proper coordination between different interfaces. Usually, there are three different kinds of software programming platforms which are taken into consideration. These are proprietary, open software and hardware independent.

Proprietary Software is the software platform provided by the vendor. This is easy to configure but is restricted to only that particular hardware platform for which it was designed.

Third party manufacturers develop hardware independent software. These are more flexible and are designed for programming on several HMI types. However, these are not very user-friendly.

In the case of the open sourced software, the platform has to be chosen by an advanced programmer only. Due to complete openness, the development is better along with better scalability.

How does an HMI relate to SCADA?

In the layman language, HMI can be called as the subsets or components of a SCADA network. With HMI, the manifestations of SCADA become even better. Using HMI can save a month of rework, development and rewriting over machine interfaces and hard-wired control panels.

Applications of HMI

HMI is deployed throughout in various industries including but not limited to vending machines, manufacturing plant, pharmaceuticals, food industry and utilities. Typically, the HMI and PLCs are backbones of the production lines. Over the years, the integration of HMIs into manufacturing has made operations efficient. HMIs are used in controlling manufacturing line processes such as efficiency, speed, error correction, and detection.

Advantages of HMI

• Due to its graphical interface, HMI is very user-friendly. There is color coding for convenient identification and pictures for quick recognition.
• HMI bring down the costs of product manufacturing significantly, thereby increasing profit margins and lowering of production costs.
• HMIs also offer kinaesthetic human and machine interaction with highly interactive and innovative functionalities


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