A human machine interface (HMI), also called an operator panel or operator interface terminal, is the screen the operator uses to start a machine, change a setpoint and read an alarm. When it goes dark, the line may still be running but nobody can control it or see why it faulted. MT.parts keeps 120+ HMIs and operator panels in stock from the leading industrial brands, including terminals the manufacturer has discontinued.
Where these operator panels are used
- Machine-mounted operator stations on packaging, filling and labeling equipment.
- Food and beverage washdown areas, where a sealed front and a stainless enclosure are required.
- Water and wastewater pump stations, for local control and trending at the skid.
- Automotive assembly and weld cells, showing cycle status, faults and part counts.
- Machine tools and shop floor equipment, where a keypad panel survives oil, chips and gloves.
- Warehouse and material handling stations, for sortation status and manual overrides.
How to choose a replacement HMI
Two panels with the same screen size are often not interchangeable. Check these before ordering:
- Part number first. The exact catalog number and series letter on the back label is the safest match. Search it in our catalog.
- Screen size and input type, for example 5.5 in, 6 in, 10.4 in and 12.1 in wide, in touch only, keypad only or keypad plus touch versions.
- Resolution and format, standard versus widescreen, because a wide unit changes the aspect ratio and the existing screens have to be redrawn.
- Panel cutout and enclosure rating, since a different bezel means a new cutout, and washdown areas need a front rated for it.
- Communication ports and drivers, Ethernet, serial, DH-485 or similar, so the panel still talks to the PLC that is already installed.
- Power input and configuration, 24 V DC versus 120/240 V AC, and whether you need a complete terminal or only the display module of a two-part unit.
If you are unsure which code replaces yours, send us the nameplate data and our team identifies the correct unit.
New, refurbished and obsolete HMIs
We supply three conditions, and the condition is always stated on the product page. New units are factory-sealed. Refurbished units are inspected, repaired where needed and functionally tested before shipping. Obsolete and hard-to-find panels are terminals the manufacturer has discontinued, which is often the only way to keep the original screens, the original cutout and the original PLC driver in service. Every HMI we ship carries a 12-month warranty.
HMI brands and series we stock
- Allen-Bradley: PanelView 550 touch, keypad and keypad plus touch, PanelView 600 keypad and keypad plus touch, PanelView 900 touch, PanelView 1000 touch, PanelView 1000e, PanelView Plus 6 touch 10.4 in, PanelView Plus 6 keypad plus touch 10.4 in, PanelView Plus 6 touch and keypad plus touch 12.1 in wide, PV Plus 6 Compact 6 in, PanelView Plus display modules
- Siemens: operator panels and touch terminals, listed individually by catalog number
- Schneider Electric: operator terminals and touch panels, listed individually by reference
- Omron: operator interface terminals, listed individually by part number
- Mitsubishi Electric: graphic operator terminals, listed individually by part number
Frequently asked questions
What is the difference between an HMI and a PLC?
The HMI is the display layer: it shows values, alarms and trends and sends operator commands, but it does not run the machine logic. The PLC executes that logic and holds the real process data. If the machine keeps running but the screen is blank or frozen, the HMI is the suspect; if the machine itself stopped, look at the controller.
Can I replace a discontinued HMI with a newer panel?
Often the cutout, the aspect ratio and the runtime version all change, which means a new panel opening and converting the application to the newer software. Replacing with the same discontinued catalog number keeps the existing screens and the existing cutout. We stock obsolete panels for exactly that reason.
Do refurbished HMIs come with a warranty?
Yes. New, refurbished and obsolete panels all ship with a 12-month warranty.
How fast can I get a quote?
We reply to quote requests within 24 hours, including part identification when you only have nameplate data.
Do you ship internationally?
Yes. We ship worldwide, including to plants outside the United States.
Can't find your part number?
If the panel you need is not listed, we source it. Send us the manufacturer, part number and quantity, and our team locates the unit, including discontinued models. Request a quote.
