Monitoring Relays

Monitoring relays help to protect some of the most expensive and sensitive equipment in industry. They are also used to provide protection for the components in some appliances. These devices prevent machinery and electronics that are sensitive to fluctuations in the power grid by reacting to specific types of changes. Relay technology itself is not new. Relay switches have been in use for over 100 years and are basic components of electrical systems and basic tools of electrical design and engineering.

Relay switches have become much more advanced over the decades, however. This allows them to be set to very specific tolerances and, therefore, to provide excellent protection for the devices that they are used to monitor.

The Basics

Certain types of electrical equipment are very sensitive to fluctuations in the power supply that provides them with energy. For example, a phase imbalance of a couple of percent can overheat electrical motors and other devices, potentially destroying very expensive equipment. Changes in current, temperature and other variables can result in the complete loss of a piece of machinery and, along with it, the entire investment that the company made in the machinery. This is why it’s vital to make sure that devices have some level of protection that is automatic, reliable and precise.

Relays are used to protect against the following variances in the electrical supply:

  • Current fluctuations
  • Phase variances and reversals
  • Heat fluctuations
  • Voltage fluctuations
  • Frequency fluctuations

Modern power supply systems are very reliable but there are still plenty of instances where a variance is introduced into the system that is potentially damaging to machinery. This makes relays necessary equipment for most precision machinery. Aside from the hazards presented by the electrical supply provided to the machine, the machine itself can present a hazard if it has a malfunction and the load suddenly increases or decreases or other problems manifest. Relays protect the machine and the circuit from both sides and help to prevent the loss of valuable equipment.


Monitoring relays can be used in any application where a change in voltage, current, phase or another factor is a threat or where it provides valuable feedback. For instance, relays are used in alarm systems where a change in voltage indicates that a door or window has been opened or broken. The most advanced monitoring relays are usually found on factory floors, however,

Some of these relays are adjustable. They can be used to monitor different variables and to react in different ways when specific tolerances are exceeded. For example, immediately shutting down a machine may be more dangerous to the device than letting the voltage get over or under norms by a certain amounts, so the relay can be set to react only if it reaches a threshold that is well outside of tolerances. This ensures that conditions that are less than optimal, but hardly catastrophic, don

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