HMI Development Interview Questions & Answers

  1. Question 1. What Are The Basic Types Of Hmis?

    Answer :

    There are three basic types of HMIs: the push button replacer, the data handler, and the overseer. Before the HMI came into existence, a control might consist of hundreds of push buttons and LEDs performing different operations. The pushbutton replacer HMI has streamlined manufacturing processes, centralizing all the functions of each button into one location. The data handler is perfect for applications requiring constant feedback from the system, or printouts of the production reports. With the data handler, you must ensure the HMI screen is big enough for such things as graphs, visual representations and production summaries. The data handler includes such functions as recipes, data trending, data logging and alarm handling/logging. Finally, anytime an application involves SCADA or MES, an overseer HMI is extremely beneficial. The overseer HMI will most likely need to run Windows, and have several Ethernet ports.

  2. Question 2. How To Select An Hmi?

    Answer :

    An HMI is a substantial purchase, so it is important to know exactly what is required of it. An HMI is used for three primary roles: a push button replacer, data handler, and overseer. The push button replacer takes the place of LEDs, On/ Off buttons, switches or any mechanical device that performs a control function. The elimination of these mechanical devices is possible because the HMI can provide a visual representation of all these devices on its LCD screen, while performing all the same functions. The Data Handler is used for applications that require constant feedback and monitoring. Often these Data Handlers come equipped with large capacity memories. The last of the HMI three types is referred to as the overseer, because it works with SCADA and MES. These are centralized systems that monitor and control entire sites or complexes of large systems spread out over large areas. An HMI is usually linked to the SCADA system’s databases and software programs, to provide trending, diagnostic data, and management information.

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  4. Question 3. What Programming Software To Choose?

    Answer :

    When considering which programming software to use, there are three main categories to choose from: proprietary, hardware independent and open software. Proprietary software is the software that the manufacturer provides, which is typically easy to use and allows for quick development. The drawback is that proprietary software will only run on that specific hardware platform. Hardware-independent software is third party software developed to program on several different types of HMIs. This type of software gives the developer much more freedom for the HMI selection. The downside to hardware independent software is that it is not as user-friendly as the proprietary. Open Software should only be selected by the advanced programmer. It allows the developer to have complete openness in the design process.

  5. Question 4. What Are The Advantages Of An Hmi?

    Answer :

    The greatest advantage of an HMI is the user-friendliness of the graphical interface. The graphical interface contains color coding that allows for easy identification (for example: red for trouble). Pictures and icons allow for fast recognition, easing the problems of illiteracy. HMI can reduce the cost of product manufacturing, and potentially increase profit margins and lower production costs. HMI devices are now extremely innovative and capable of higher capacity and more interactive, elaborate functions than ever before. Some technological advantages the HMI offers are: converting hardware to software, eliminating the need for mouse and keyboard, and allowing kinesthetic computer/human interaction.

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  7. Question 5. How Many Different Hmi Types Are Currently Offered By Anaheim Automation And What Are The Major Differences?

    Answer :

    With just Kinco, Anaheim Automation offers three different types of HMI starting with the MT4000, ranging in sizes from; 4.3″ to 12.1,” with a 400 MHz processor. The MT5020 and MT6000 on the other hand, both contain a 520 MHz processor. The MT5020 series comes standard with Ethernet capabilities along with more ports than the MT4000. The MT6000 is the complete package, although it has the same processing power as the MT5020. This HMI comes standard with Windows CE and its own SDK, which allows the user to use any programming language to build an application. 

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  9. Question 6. What Are The Benefits Of Using Both An Hmi And Plc, As Opposed To Just A Plc?

    Answer :

    The benefits of using an HMI along with a PLC are substantial. PLCs tend to be complex, with many wires connected to them, making it difficult to find the correct input to manually toggle. With an HMI, the user can toggle PLC’s through memory, as opposed to having to re-wire. HMIs also provide a real time view of the system, so if recipe memory in the PLC was to max out, the user could easily wipe its contents without having to disconnect the PLC. 

  10. Question 7. What Is A Baud Rate?

    Answer :

    Baud, synonymous to symbols per second, or pulses per second, is often times referred to as the unit of the symbol rate. It is the number of distinct symbol changes made to the transmission medium per second in a digitally modulated signal or a line code.

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  12. Question 8. What Communication Protocols Are Applicable To Our Hmi Line?

    Answer :

    • RS232
    • RS422
    • RJ-45 
  13. Question 9. Which Plc Unit Do I Select If My Plc Is Not Listed Under Compatible Plc’s?

    Answer :

    Selecting a PLC depends on what protocol this PLC or controller uses. If the controller uses Modbus RTU, then the user should select Modbus RTU Slave. If the controller uses ASCII, then the user should select the Universal ASCII slave.

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  15. Question 10. What Is Windows Ce And What Is The Codesys Packet?

    Answer :

    Windows CE in an embedded operating system, which translate to a very stripped and minimalistic copy of windows for smaller devices such as HMIs and cellular phones. The Codesys packet is a proprietary third party software, which will give allow the user to program an HMI and PLC. 

  16. Question 11. What Type Of Touch Panel Do These Kinco Hmi’s Use?

    Answer :

    TFT, which stands for Thin Film Transistor.

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  18. Question 12. How Many Controllers Can I Hook Up To One Hmi?

    Answer :

    As many COM ports as that specific HMI has.

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  20. Question 13. What Programming Language Comes Standard With The Ev5000?

    Answer :

    ANSI C89

  21. Question 14. Do Hmis Have Printing Capabilities?

    Answer :

    It varies depending on the manufacturer. Some HMIs will come with specific printers that are compatible, while others will not have printing capabilities. Some HMIs have the capability to install the user’s own drivers for the printer of choice.

  22. Question 15. How Does One Program An Hmi?

    Answer :

    There are a few third party programs that can be used to create an HMI graphical user interface, such as CodeSys and EV5000. Some HMIs come standard with their own proprietary software, which provides the functions specific to that HMI. Lastly, some HMI’s come with SDK packages so the user can program the HMI in his/her native language. 

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  24. Question 16. What Are The Benefits Of An Hmi Over A Desktop?

    Answer :

    An added benefit of an HMI is that it is application-specific. In other words, a panel will not allow for internet browsing, solitaire game play, or update reminders unless it pertains to the task at hand. HMIs provide absolute control; meaning that you may give the user limited access to specific features, or full access depending on how the interfaces are created. (See Advantages of an HMI).

  25. Question 17. What Does Hmi Stand For?

    Answer :

    Human Machine Interface

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