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. 124-0193
Mfr. Part No.RM35LM33MW
HK$735.64
Each
units
Level 20.4 → 264 V ac/dc DPDT - 1 - - - - - 0.1 → 5 s - - -
RS Stock No. 145-976
Mfr. Part No.RM35JA32MW
HK$1,727.43
Each
units
Current 24 → 240 V ac/dc DPDT - - - Overcurrent, Undercurrent 0.15A 15A - 0.3 → 30 s - - -
RS Stock No. 146-480
Mfr. Part No.RM35TF30
HK$2,350.23
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. 146-238
Mfr. Part No.RM17TG20
HK$987.87
Each
units
Phase 208 → 440 V ac DPDT - 3 - - - - Phase Asymmetry, Phase Failure, Phase Sequence <100 ms - - -
RS Stock No. 146-597
Mfr. Part No.RM17TU00
HK$1,299.72
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. 146-171
Mfr. Part No.RM17UAS15
HK$1,390.60
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. 146-200
Mfr. Part No.RM35JA31MW
HK$1,137.94
Each
units
Current 24 → 240 V ac/dc DPDT - - - Overcurrent, Undercurrent 2mA 500mA - 0.3 → 30 s - - -
RS Stock No. 146-070
Mfr. Part No.RM35S0MW
HK$2,049.83
Each
units
Speed 24 → 240 V ac/dc SPDT - - - - - - - 0.6 → 60 s - - -
RS Stock No. 146-086
Mfr. Part No.RM35BA10
HK$2,000.01
Each
units
Current, Phase 208 → 480 V ac, 230 V ac SPDT - 1, 3 - Overcurrent, Undercurrent 1A 10A Phase Failure, Phase Sequence 0.1 → 10 s - - -
RS Stock No. 146-193
Mfr. Part No.RM35HZ21FM
HK$1,678.17
Each
units
Frequency 120 → 277 V ac DPDT - - - - - - - 0.1 → 10 s - - 40 → 70 Hz
RS Stock No. 146-474
Mfr. Part No.RM35UB330
HK$1,804.61
Each
units
Voltage 220 → 480 V ac DPDT Absence of Neutral, Overvoltage and Undervoltage Between Neutral, Overvoltage and Undervoltage Between Phase 3 194 → 528 V ac - - - - 0.3 → 30 s - - -
RS Stock No. 146-608
Mfr. Part No.RM17TT00
HK$988.51
Each
units
Phase 208 → 480 V ac SPDT - 3 - - - - Phase Asymmetry, Phase Failure, Phase Sequence 0.1 → 10 s - - -
RS Stock No. 175-3712
Mfr. Part No.R9PCR
HK$1,019.77
Each
units
Current, Voltage 250 V ac 1P+N - 1+N - - - 5A - - - - -
RS Stock No. 124-0189
Mfr. Part No.RM22UA33MT
HK$1,664.90
Each
units
Voltage 323 → 456.5 V ac DPDT Overvoltage, Undervoltage 3 15 → 500 V ac/dc - - - - 0.1 → 30 s - - -
RS Stock No. 124-0182
Mfr. Part No.RM22LG11MR
HK$586.21
Each
units
Level 20.4 → 264 V ac/dc SPDT - 1 - - - - - <0.6 (Run-Up) s - - -
RS Stock No. 179-9431
Mfr. Part No.RM22TA31
HK$1,229.89
Each
units
Phase 200 → 240 V ac DPDT Overvoltage 3 <100 V ac - - - - 30 s - - -
RS Stock No. 609-8075
Mfr. Part No.LT3SM00ED
HK$3,843.84
Each
units
Temperature 24 → 48 V dc SPDT - - - - - - - - Overtemperature, Undertemperature - -
RS Stock No. 179-0019
Mfr. Part No.RMNF22TB30
HK$1,402.30
Each
units
Frequency, Voltage with NFC 208 → 480 V ac - - 3 - - - - - - - - -
RS Stock No. 124-0183
Mfr. Part No.RM22LG11MT
HK$701.15
Each
units
Level 323 → 456.5 V ac DPDT - 3 - - - - - <0.6 (Run-Up) s - - -
RS Stock No. 179-9435
Mfr. Part No.RM22UA23MR
HK$1,264.38
Each
units
Phase 24 → 240 V ac/dc DPDT Overvoltage 1 15 → 500 V ac/dc - - - - - - - -