Monitoring relays

SIRIUS monitoring relays provide reliable protection for machines and plants. Current measured values or conclusive diagnostics messages are indicated on the device display. For easy connection to the controller, most monitoring relays are also available with an IO-Link interface. We offer monitoring relays for electrical and mechanical variables, as well as temperature monitoring.

Technical specifications for monitoring relays

Industry Mall

SIRIUS monitoring relays - one range for every application


Monitoring of line, current, voltage, power factor and active current, residual current, insulation, level, and speed

SIRIUS 3UG4 monitoring relays for electrical and mechanical variables

SIRIUS 3UG4 monitoring relays monitor the most diverse electrical parameters in the feeder, and provide reliable protection against damage in the plant. They not only feature parameterizable threshold values and manifold adjustment options, but also provide conclusive diagnostics, being able to correct an incorrect phase sequence autonomously. Numerous versions are also available with IO-Link interface for connection to the controller.


The SIRIUS 3UG4 monitoring relays also monitor mechanical variables.

The level monitoring relays ensure reliable 1 or 2-point controls and alarm messages in the event of overflow or dry running.

The speed monitoring relays check whether the nominal speed of motors, shafts or powered wheels is exceeded or not reached. Moreover, the relays are suitable for all functions requiring the monitoring of a continuous pulse signal. Optionally with IO-Link connection.


For direct mounting on contactors for multi-phase current monitoring

SIRIUS 3RR2 monitoring relays for electrical variables

The SIRIUS 3RR2 current monitoring relays are especially designed for optimum current monitoring of the overall plant or of the powered process. Thus, load shedding or overload of the motor, for example, is detected quickly and reported early. The 3RR2 monitoring relay for current monitoring is integrated directly in the load feeder. It simply plugs into the contactor. Also available with IO-Link connection.


Protection against overheating in windings

SIRIUS 3RN2 thermistor motor protection relays

SIRIUS 3RN2 thermistor motor protection relays directly monitor a motor’s winding temperature and thus ensure reliable protection against overheating. Under atypical conditions, such as heavy starting or inadequate cooling, a motor is at extreme risk of overheating. With the SIRIUS 3RN2, you can relax, assured that production systems will be monitored reliably, even under difficult conditions.


Temperature monitoring

SIRIUS 3RS1/2 temperature monitoring relays

The temperature of solid, liquid and gaseous media represents the most frequently measured parameter in industrial applications. The SIRIUS 3RS1 temperature monitoring relays monitor process temperatures just as reliably as the temperatures in control cabinets or of motors - with up to three sensors at the same time where required.  These are available in analog or digital versions (also with IO-Link).


Analogically adjustable: The temperature is recorded by sensors in the medium, evaluated by the device, and monitored to determine whether it is within the upper and lower temperature limits. When the threshold values are reached, the output relay switches on or off depending on the parameterization.


Digitally adjustable: The temperature is monitored to evaluate whether it is above or below a certain value or within a specific operating range (window function). These devices also present a good alternative to temperature controllers in the low-end range.

We offer you different monitoring relays, depending on your requirements

Videos on functions of the monitoring relays

  • Line and single-phase voltage monitoring (also via IO-Link)
  • Multi-phase current monitoring (also via IO-Link)
  • Single-phase current monitoring or power factor and active current monitoring (also for IO-Link)
  • Level monitoring
  • Speed monitoring