Alarming & Messaging


Thread Starter

Rob Dombek

I would like to get input/suggestions for displaying alarms, messages and faults. I'm really looking for any references, guidelines, books, etc. that may describe methods for creating machine failure messages from the PLC to HMI. I have done this many times, but know that my method(s) may or may not be better than anyone elses. I worked for an OEM company that supplied the automotive industry with wheel alignment machines and typically Ford, Chrysler, etc. would have a specification book on what and how alarms were displayed and acknowledged. The
spec's were supposed to be corporate-wide, but in reality each plant was different. Sometimes we would just display messages, sometimes if
there was a fault, the machine was not allowed to continue to the next step until the fault was corrected. I am doing research on this subject and will probably be including this topic in my book for our company. Any input is greatly appreciated!
An OK text "HMI Desgin Guide" April 1997, from Advanced Automation Associates, Inc. has guidelines for user interface design and standardization. There are a few Alarm examples in the book. In the real world depending on the HMI package you use, the look and feel will vary.
Hi Rob! There are (really) many methods for creating alarms between PLC and HMI. One method is, just consider tags inside the PLCs that you
can use as an alarm in the HMI. It's either just an ordinary alarm or an interlock. It's also either you make it in the PLC or just in the
HMI. Mr Kostur is right. Depending on what you use, the look and feel will vary, and also the ease in programming. If you want a better
method in capturing alarms, use MSSql from Microsoft (or other vendors like Wonderware and RSView). These softwares will log how many times
the machine bugs down, when did it occur, etc.
In our application we use Wonder Ware as our HMI. The alarms are generated in the PLC, and the tagname that we entered in the Wonder Ware application is displayed. We also use Wonder Ware SQL Server for logging faults and alarms for

As far as locking out the functions until the alarm is cleared, we do all of that in the PLC so that even if the HMI computer is knocked out, we have control of the machine.

Hope this helps.


Clive Mountain

Another aspect you should consider is the modularisation of the code in the PLC/Control System. If the code is modularised, it can be re-used many time on other machines, and remain the same. This way, any engineers looking at the
code will be familiar with the alarm handler in the PLC. We've done the same for many similar functions such as Recipe Handling etc.

Consider structuring alarms, and perhaps prioritising. You don't want nuisance alarms to occur just because another alarm occures. e.g. When you hit an emergency stop, you don'y wand inverter drive faults appearing as a

If anyone has a decent PLC alarm handler, let me know.

Zan Von Flue

I used Alarm tags in the PLC. This also makes it easier to change HMI/SCADA types. Easier even if you have more then one HMI connected. I also feel the display construction should also be in black and white or in with a minimum of colors. Color can always be added later for frames etc. Yellow, red colors, and blinking information should also be at a minimum. I have both B/W and color displays. But the button position and information are in the same basic position. It makes it easier to transfer the display overlayer.


Gianluca Petrocchi (Italy)

Hi Rob, I think one one the best method is to trig an alarm as a change-of-state of an associated variable or "tag" in the PLC. In many
SCADA editors, such as RSView32 (the one I usually use), you can configure the entire alarm handling and pre-determinate whenever an alarm
event will be triggered and logged in the database. If I have well understood, you ask for a way to acknoweledge an alarm state and do not
stop the automatic cycle. About this, I think is better to let the PLC determinate the stop conditions, even with different priorities, and
the HMI visualize the alarms and keep a trace of them. Finally, you can look at "" and download some manual. Sorry for my bad english. Bye

Leonard Hamilton

I have the impression that you are asking about "alarm management" rather than programming methodology. In that case I can think of two places where you might recieve information. Beville Engineering and Honeywell IAC. Hope this helps.