The line of Macromatic current sensing relays currently available through Major Electronix has changed to include versions with encapsulated housings. This takes the place of the previously offered plug-in style current sensing relays. Also known as current monitoring relays, they are made to protect equipment that would be susceptible to damage or performance problems in the event of an improper current fault, such as a conveyor jam up. They can be used for monitoring overcurrent or undercurrent situations, or both. The encapsulated housing is ideal for harsher environments, while the relays themselves are designed to check single phase AC current.

There are three series of Macromatic current sensing relays. The COH series checks for overcurrent conditions, the CUH series monitors undercurrent situations, and the CAH series has a switch that allows the user to select which fault the relay should be monitoring. All of them feature adjustable fault trip currents within a certain range (0.5-5A, 2-20A, or 5-50A), and adjustable trip time delays (0.15-7 seconds or 0.5-50 seconds). Input voltage can vary depending on the unit, with 12V, 24V, 120V, and 240V versions. There is a time delay on startup which can range from 1-6 seconds. Units are also available without a startup time delay. All units also have an integrated toroidal current transformer for quick access, and an LED indicator which glows red to show a fault.

Macromatic current monitoring relays will start checking for faults as soon as the input voltage is introduced and the startup time delay has passed. When the AC current goes above or below the set Fault Trip Current, and stays there for a longer period than the set Trip Time Delay, the relay becomes energized and the LED glows. When the AC current goes back to the proper level, the LED will shut off and the relay de-energizes.

Some common applications include checking heater or lamp load status, monitoring for a locked rotor, detecting possible load loss, and process control. Material handling, packaging equipment, generator control, and food & beverage packaging are all areas that can benefit from a current sensing relay.