What is a measuring and monitoring relay?

A measuring and monitoring relay, also known as an alarm relay, is a protective control device which can receive input signals, monitor and determine them, and output an alarm signal if a set value or threshold is reached.


Measuring and monitoring relays protect your important devices and products against overvoltage or overcurrent faults. They monitor AC power supplies (voltage and current), temperatures, and other analog signals and detect abnormalities in machines and equipment by determining values against alarm thresholds. An alarm signal can be output from relay contacts if an input signal goes into an abnormal status to stop the machine or equipment before it is damaged.


Types of measuring and monitoring relays

OMRON offers a wide range of relays including industrial temperature monitors, measuring and monitoring relays and phase control relays. Which type of measuring and monitoring relay you choose will depend on what you want to monitor. Here’s a brief overview.


Motor protection relays: ideal for monitoring error trends in motors and other equipment. OMRON offers several series under this product family:

- K8DT-AW monitoring relay ‘Push-In Plus’ terminal, which detects errors in motors and other equipment through current changes.

- K8DT-PZ 3-phase monitoring relay ‘Push-In Plus’ terminal, which protects motors and other equipment from unstable voltages in the power supply system.

- K8DT-VW voltage monitoring relay terminal which detects abnormal voltages applied to equipment to protect against equipment failure.


Temperature monitoring relays: ideal for redundant prevention of excessive temperature increases in heaters.

- The K8DT-TH temperature monitoring relay is ideal to prevent heater overheating.


Water level control: ideal for water level detection and control in tanks. OMRON offers two series under this product family:

- K8DT-LS conductive level controller, which is great for water level control. It has sensitivity adjustment from 10k to 100 kΩ and ON-delay timer from 0.1 to 10s.

- K8AK-LS conductive level controller series is ideal for liquid level control in industrial facilities and equipment. It prevents chattering of relay contacts that occurs with ripples.


See our comprehensive range of measuring and monitoring relays below. For more information, read our technical guide or contact us today.