What are alarms?

The name alarm will normally conjure up images of flashing lights and critical errors on your machine. In many cases, this is exactly what alarms are used for – their main purpose is to relay information to the operator. As we will see later on in the chapter, in the section Alarm configuration: Info, Warning, and Error setup, alarms relay way more information than just catastrophic errors.

For most PLC applications, alarms have two sections. The first component of an alarm is the PLC logic itself. The PLC logic is the code that will trigger the alarm. The other section is the HMI component that will display the alarm in a logical, user-friendly manner. Therefore, before you can start using alarms, you’re going to want to ensure that you have a decent understanding of PLC programming and HMI layouts for your custom alarms to work.

Alarms are multifaceted. Not only can they display information to the operator, but with the right PLC logic, they can...