As with any big purchase, it is often difficult to choose the “best” option. I sometimes drive myself crazy researching my options and trying to determine how to get the most bang for my buck. Well, as many of my clients have shared with me, there are times when it isn’t easy to select the appropriate HMI (Human Machine Interface) for their application. In an effort to make the HMI selection process a bit less daunting, I have included several important points below that I hope will help make the selection process easier!
How to choose an HMI:
- Determine the screen size: How much space do you have in your panel for an HMI unit? If you are running SCADA software, the screens must be developed to fit the size of an HMI. A larger HMI will result in fewer screens to develop, while a 6”-7” will leave you with more.
- Determine the touch type: Will your application work with a standard touch screen or does it need an Elo touch interface to operate? In addition, is 5-wire resistive enough (it usually is) or is capacitive the way to go?
- Determine the resolution: Some software applications require a specific screen resolution to successfully operate. You will need to determine what that is and select the appropriate HMI based on the requirements.
- Determine if you will implement an all-in-one solution: Are you comfortable implementing an HMI solution that includes screen, CPU, memory, storage and operating system or would you rather have a separate HMI from the PC? This will depend on the usage and physical treatment of the HMI. If workers are rough on the units, it might be best to select a solution that includes a screen and separate embedded PC. This will enable you to swap out damaged screens as needed.
- If using an all-in-one unit: Make sure that you determine whether the HMI will act as the main pass through for all information back to the server(s). If so, make sure you have the appropriate I/O (RS-485, GbE LAN, USB, etc.) to successfully interface with the PLC and other external I/O for communications purposes.If this isn’t the case, it’s still a good is to have 1-2 GbE LAN ports and at least one RS-485 port.
Still feeling unsure? I’d be glad to talk you through some of these options and help you narrow down the best solution for your requirements. Give me a call at 1-800-830-9523.