Monitoring Relays

Monitoring relays are a type of relay that trips a circuit breaker when a fault is detected. A relay is an electrically controlled switch that is used to turn the power on or off in a circuit. 


Monitoring relays are more sophisticated than regular relays, as they have adjustable operating conditions, whereas normal relays switch according to a fixed threshold. They measure a given parameter, such as voltage or temperature, and will trip a circuit breaker when the parameter gets too high or low. 


What are monitoring relays used for?

Monitoring relays have a wide range of uses, depending largely on the factor being monitored. For example, they can protect against overcurrent if measuring current, or they can detect an abnormally low frequency if frequency is being measured.


Types of monitoring relay

The main way in which monitoring relays differ is the function that they measure. This can be a number of things, including:

  • voltage
  • current
  • temperature
  • frequency

The factor that you need to measure will decide which monitoring relay you choose.


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Description Price Monitoring Application Supply Voltage Contact Configuration Voltage Sensitivity Electrical Phase Voltage Sensing Range Current Sensitivity Minimum Current Sensed Maximum Current Sensed Phase Sensitivity Time Delay Temperature Sensitivity Temperature Sensing Range Frequency Sensing Range
RS Stock No. 102-6134
BrandRS PRO
£69.83
Each
Units
Current 24 → 230 V ac/dc SPDT - 1 - Overcurrent, Undercurrent 1A 10A - 0.1 → 30 s - - 48 → 63 Hz
RS Stock No. 102-6130
BrandRS PRO
£35.35
Each
Units
Voltage 12 → 24 V dc SPDT Undervoltage 1 12 → 24 V dc - - - - 0 → 30 s - - -
RS Stock No. 102-6135
BrandRS PRO
£37.86
Each
Units
Phase, Voltage 280 → 520 V ac SPDT Undervoltage 3 Maximum of 280 V - - - Phase Failure, Phase Sequence 100 ms - - 48 → 63 Hz
RS Stock No. 102-6133
BrandRS PRO
£69.83
Each
Units
Voltage 24 → 230 V ac/dc SPDT Overvoltage, Undervoltage 1 50 → 500 V - - - - 0.1 → 30 s - - 48 → 63 Hz
RS Stock No. 102-6137
BrandRS PRO
£51.22
Each
Units
Phase, Voltage 400 V ac SPDT Overvoltage, Undervoltage 3 300 → 380 (Undervoltage) V, 420 → 500 (Overvoltage) V - - - Phase Failure, Phase Sequence 0.2 → 10 s - - 48 → 63 Hz
RS Stock No. 102-6131
BrandRS PRO
£39.81
Each
Units
Voltage 230 V ac SPDT Overvoltage, Undervoltage 1 173 → 218 (Undervoltage) V, 242 → 288 (Overvoltage) V - - - - 0.2 → 10 s - - 48 → 63 Hz
RS Stock No. 102-6136
BrandRS PRO
£39.81
Each
Units
Phase, Voltage 280 → 520 V ac SPDT Undervoltage 3 300 → 500 (Undervoltage) V - - - Phase Failure, Phase Sequence 0.2 → 10 s - - 48 → 63 Hz
RS Stock No. 146-238
Mfr. Part No.RM17TG20
£78.00
Each
Units
Phase 208 440 V ac DPDT - 3 - - - - Phase Asymmetry, Phase Failure, Phase Sequence <100 ms - - -
RS Stock No. 240-8939
Mfr. Part No.BA9043 3AC50-400Hz 230/400V
BrandDold
£164.72
Each
Units
Voltage 230/400 V ac DPDT Undervoltage - - - - - - - - - -
RS Stock No. 146-171
Mfr. Part No.RM17UAS15
£97.24
Each
Units
Voltage 110 → 240 V ac/dc SPDT Overvoltage, Self Powered, Undervoltage 1 65 → 260 V ac/dc - - - - 0.1 → 10 s - - -
RS Stock No. 518-7297
Mfr. Part No.3UG4513-1BR20
BrandSiemens
£96.77
Each
Units
Phase, Voltage 160 → 690 V ac DPDT Undervoltage 3 160 → 690 V ac - - - Phase Failure, Phase Imbalance, Phase Sequence 0.1 → 20 s - - -
RS Stock No. 146-480
Mfr. Part No.RM35TF30
£172.00
Each
Units
Phase, Voltage 220 → 480 V ac DPDT Overvoltage, Undervoltage 3 194 → 528 V ac - - - Phase Asymmetry, Phase Failure, Phase Sequence 0.1 → 10 s - - -
RS Stock No. 347-696
Mfr. Part No.FSRST30SLP-110/230VAC
BrandTempatron
£67.00
Each
Units
Shaft Rotation Sensor 110 V ac, 230 V ac SPDT - - Maximum of 30 V dc - - - - 1 → 30 s - - 50 → 60 Hz
RS Stock No. 145-976
Mfr. Part No.RM35JA32MW
£120.00
Each
Units
Current 24 → 240 V ac/dc DPDT - - - Overcurrent, Undercurrent 0.15A 15A - 0.3 → 30 s - - -
RS Stock No. 850-5370
Mfr. Part No.LXPRT 280-520VAC
£51.52
Each
Units
Phase, Voltage 280 → 520 V ac SPDT Undervoltage - 300 → 500 V - - - Phase Failure, Phase Sequence 0.2 → 10 s - - -
RS Stock No. 124-0193
Mfr. Part No.RM35LM33MW
£64.00
Each
Units
Level 20.4 → 264 V ac/dc DPDT - 1 - - - - - 0.1 → 5 s - - -
RS Stock No. 518-7168
Mfr. Part No.3UG4622-1AW30
BrandSiemens
£110.02
Each
Units
Current 24 → 240 V ac/dc SPDT - 1 - Overcurrent, Undercurrent 50mA 10A - 0.1 → 20 s - - -
RS Stock No. 146-597
Mfr. Part No.RM17TU00
£83.00
Each
Units
Phase, Voltage 208 → 480 V ac SPDT Undervoltage 3 183 → 528 V ac - - - Phase Failure, Phase Sequence 0.1 → 10 s - - -
RS Stock No. 857-7075
Mfr. Part No.DIA53S72420A
£37.44
Each
Units
Current - SPST - 1 - Overcurrent - - - <300 ms - - -
RS Stock No. 518-6070
Mfr. Part No.817-E1
£80.90
Each
Units
Temperature 24 → 240 V ac/dc DPST - - - - - - - - Overtemperature - -
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