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What is MMI?
Could anyone tell me what MMI stands for and what it's application is?
By Anonymous on 20 May, 2003 - 5:03 pm

Could anyone tell me what MMI stands for and what it's application is?

By Anonymous on 20 May, 2003 - 9:10 pm

Reply: (a) Man-Machine Interface
(b) MicroMotion, Inc (part of Emerson Process Management)

By Steve Myres, PE on 20 May, 2003 - 9:11 pm

It stands for "Man-Machine Interface" and, as you may gather from the name, is the hardware and/or software which allows the operator, engineer, etc. to control and monitor the machine function, as opposed to the hardware and/or software that contains the logic by which machine operation is controlled. You will also see "HMI" used, for "Human-Machine Interface".

By Daniel Chartier on 20 May, 2003 - 9:20 pm


In automation circles the terms MMI (Man-Machine Interface) and HMI (Human-Machine interface) are used interchangeably. They define text- or graphics-based displays that allow operators to visualize the values of PLC registers on the plant floor (speed of conveyor belts and motors, temperature of furnaces, levels and flow of liquids...); they also allow writing of setpoint values and start/stop commands to the PLC.

Another term that relates to MMI is SCADA (Supervisory Control and Data Acquisition); they are generally computer-based packages (Wonderware, WinCC, IFix...) that allow the same control and display as MMIs, but also permit interfacing to databases. This allows archiving and trending of process values, alarm monitoring, animations and web interfacing, among others.

Hope this helps,
Daniel Chartier

By Tom Wiesen on 20 May, 2003 - 9:34 pm

Man Machine Interface

The more politically correct version is Human Machine interface. Anything used to interface with a human being. Generally, could be a touch panel, a push button panel, indicating light, etc. Most often used to refer to an electronic display such as a video computer monitor or touch screen computer. Companies such as Eaton, Siemens, and Allen Bradley make HMI software that runs on a PC or dedicated display terminal. Programs are generally written off line and downloaded to the industrial display.

C. Thomas Wiesen

By Hugo Ahrens on 22 May, 2003 - 6:38 pm

This is all a great misunderstanding!

The term MMI actually stands for "Mammal Machine Interface". Since this term is clearly more encompassing than the politically correct touted HMI, I suggest we all stand by the original term MMI.

Of course as with any subject, there are local aberrations such as:
LOI Local Operator Interface
ROI Remote Operator Interface
OI Operator Interface

The thing that should be consistent, is the underlying meaning that when you are talking about the MMI you are not talking about the control of the machine/system, but rather only about the component of the system dealing with interfacing to the mammal.


By Chad Markovich on 21 May, 2003 - 10:59 am

MMI means "Man-Machine Interface." MMI's are used to provide control and status for automated systems. For example, this could be the screen that a machine operator uses to start a machine cycle, or set the number of cycles the system needs to run, or see the reason why the system stopped, and so on. These used to be boards made up of pilot lights, pushbuttons, and selector switches, and you still see these on many older systems. However, the cost of all those individual pilot lights, pushbuttons, & the cost to wire them back to a controller is usually more expensive than most solid-state type MMI's today. Plus, the MMI screens take up less space and can be changed relatively easily compared to push button stations, especially when adding more lights & buttons to a system. By the way, each pilot light & push button needs to be wired up to it's own I/O point (and sometimes to more than one I/O point) on a controller, which usually increases the amount of controller I/O modules required for your system, which increases the system cost.

The term "MMI" has been replaced with "HMI" (Human-Machine Interface) for political correctness, I guess. You will also hear "MMI" being referred to as "OI" (Operator Interface), "OIT" (Operator Interface Terminal), "SCADA" (Supervisory Control And Data Acquisition) - but SCADA usually refers to a higher level system than that of MMI's. Based on the system in which they are used, HMI's may actually do the control, or some of the control, or they just may be looking at specific data points from the actual controller devices, commonly referred to as PLC's (Programmable Logic Controllers.)

It's a deprecated mnemonic for Man-Machine-Interface. Now the proper term is HMI which is the unisex Human-Machine-Interface.

The name describes the function in either case. It encourages and interprets human actions and transforms them into actions/data the machine can understand and translates the machine actions/data into a form the human can understand.

For example, your keyboard, crt and mouse are all HMI (hardware) components.

The software that captures keyboard and mouse input and displays stuff on the crt are all HMI (software) components.

If you talk about UIs (User interfaces) or GUIs (Graphical User Interfaces) you're also talking about the same thing.


By Rocco F. Dominick on 21 May, 2003 - 6:36 pm

MMI refers to Man-Machine Interface which has been replaced by the more politically correct HMI - Human-Machine Interface.


If you want to go further, here's a free sample of Allen-Bradley's RSView32 system which you might be interested in. Go to:

Click the "Go!" button next to "View Current Order" and then order item number 9398-VW32STCD. This is a free CD with a (more-or-less) fully-functional copy of AB/Rockwell's RSView32 software. It has a decent tutorial and online reference manuals to get you started and lots of interesting samples to play with. (Once you've played with these for awhile, start dissecting them to learn how they work. This is an EXCELLENT way to learn.) The catch? The demo only works for two hours at a time... but you can always save your work and just restart it over and over.

Once you have one of these CDs, you can legally load the program on many computers - it doesn't require an "activation" to run in the demo mode.

Best regards, Ron

PS - While you're at it, also order 9392-CL001B-EN-C. This is a free set of two CDs with many PLC technical manuals. Excellent reference resource for times when you can't get access to the AB Web site.

You could still be "politically" correct if you use -- Mammal-Machine-Interface ! ! ! !

I just wanted to thank all of you that responded to my question about MMI. The response was more than abundant. This was my first experience with Nerds in Control but it will definately not be my last. Thanks to all......WC

1 out of 1 members thought this post was helpful...

I always wondered why "Human Machine Interface?" It implies that perhaps there could be an CMI for a chimp, or FMI for a fish.

Remember they are panel operators, too!

Phil Corso, PE
Boca Raton, FL
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A couple of years ago, it was decided here that MMI could best stand for Mind-Machine Interface - covering the chimp and goldfish situation - also including Moron-Machine-Interface.