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The GM420 series loop monitor is designed to monitor the resistance of PE conductor connections in AC systems and in de-energised systems. The extraneous voltage Uf between the terminals E and KE must not exceed AC 12 V. The ohmic resistance of the conductor loop and the AC extraneous voltage Uf, if existing, will be indicated on the display. The currently measured value is continuously indicated on the LC display. If the measured resistance value increases above the set response value, the alarm will be activated and stored. Adjustable time delays allow installation-specific requirements to be considered.

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  • Loop monitoring of the PE conductor in AC systems
  • Measuring circuit providing a high resistance against extraneous voltages and indication of extraneous voltages
  • Adjustable start-up delay, response delay and delay on release
  • Adjustable switching hysteresis
  • Digital measured value display via multi-functional LC display
  • Preset function (automatic setting of basic parameters)
  • LEDs: Power On, Alarm 1, Alarm 2
  • Measured value memory for operating value
  • Continuous self monitoring
  • Internal test/reset button
  • Two separate alarm relays with one changeover contact each
  • N/C or N/O operation and fault memory behaviour selectable
  • Password protection for device setting
  • Sealable transparent cover
  • Two-module enclosure (36 mm)
  • Push-wire terminal (two terminals per connection)
  • RoHS compliant
  • Loop monitoring of motors
  • Loop monitoring of PE conductor connections for wire interruptions in electrical installations
  • Monitoring of earthing systems


Optional accessories for LINETRAXX® GM420

TypeArt. No.
Mounting clip for screw fixing (1 piece per device, accessories)B98060008

Variants of LINETRAXX® GM420

TypeMeasuring range
Loop resistance
Measuring range
Interference voltage
Supply voltage USArt. No.*
GM420-D-10…100 ΩAC 0…50 VDC 9,6 V…94 V /
AC 16…72 V, 15…460 Hz
GM420-D-20…100 ΩAC 0…50 VDC 70…300 V /
AC 70…300 V, 15…460 Hz
*(B7… = push-wire terminal / B9… = screw-type terminal)

Downloads for LINETRAXX® GM420



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