As such, some might argue that вЂњhardвЂќ alarms are not necessary. Most every plant performs alarm functions using вЂњsoftвЂќ alarms within their DCS or PLC. This termВ differentiates a вЂњhardвЂќ alarm trip from the software-implemented alarm (a вЂњsoftвЂќ alarm) which is found within a Distributed Control System (DCS) or a programmable logic controller (PLC). Here are just some:Д«ecause they are hard-wired into the process and provide relay outputs, independent limit alarm trips are often referred to as вЂњhardвЂќ alarms. In fact, todayвЂ™s highly flexible and versatile alarm trips can be found working in a wide range of applications, under an impressive list of pseudonyms. While limit alarm trips are best known as a sure way to activate a warning light, siren or bell when a process problem occurs, they are also called upon to do much more. If the process signal moves to an undesirable high or low condition, the alarm activates a relay output to warn of trouble, provide on/off control or institute an emergency shutdown. A limit alarm trip can trigger the response needed to maintain normal, and safe, operations.ДЄ limit alarm trip monitors a process signal (such as one representing temperature, pressure, level or flow) and compares it against a preset limit. Alarm/Trip : Something happens-a signal peaks or falls-and you need to know.

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