• Insulation monitoring device for AC and DC IT systems
  • Application main circuits with connected frequency converters
  • According to IEC 61557-8
  • Automatic adaptation to the system leakage capacitance
  • Info button to display the device setting

The ISOMETER® of the IRDH275 series is designed to monitor the insulation resistance of unearthed main circuits (IT systems) AC, AC / DC 0…793 V resp. DC 0…650 V. The AMPPlus measuring principle meets the particular requirements of modern power supplies which often include rectifiers, converters, thyristor-controlled DC drives and directly connected DC components. In these systems often high leakage capacitances against earth occur due to interference suppression measures. The IRDH275 automatically adapts itself to the existing system conditions.

In combination with a coupling device, the Isometers can also be used for higher voltages. An external supply voltage allows de-energized systems to be monitored too. For door mounting into distribution panels, refer to type IRDH375(B).

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  • Insulation monitoring for unearthed AC, AC/DC systems 0…793 V, DC 0…650 V
  • Nominal voltage extendable via coupling device
  • Two separately adjustable response values1 kΩ…10 MΩ
  • AMPPlus measurement method
  • Automatic adaptation to the system leakage capacitance
  • Info button to display device settings and system leakage capacitance
  • Self monitoring with automatic alarm
  • Automatic self test, selectable
  • Connection for external kΩ indication
  • Test and reset button
  • Connection external test/reset button
  • Two separate alarm relays with two voltage-free changeover contacts
  • N/O or N/C operation
  • Backlit LC display
  • RS-485 interface
  • AC, DC or AC/DC main circuits
  • AC/DC main circuits with directly connected DC components, such as rectifiers, converters, and thyristor-controlled DC drives
  • UPS systems, battery systems
  • Heaters with phase control
  • Installations including switch-mode power supplies
  • IT systems including high leakage capacitances
  • Coupled IT systems


Optional accessories for ISOMETER® IRDH275

External kΩ measuring instrument 400 µA
TypeArt. No.

External kΩ measuring instrument 20 mA
TypeArt. No.

Coupling devices
TypeNominal system voltage UnArt. No.
AGH150W-4DC 0…1760 VB98018006
AGH204S-4AC 0…1650 (1300) VB914013
AGH520SAC 0…7200 VB913033

Variants of ISOMETER® IRDH275

TypeNominal voltage UnSupply voltage USArt. No.
IRDH275-435AC 0…793 V / DC 0…650 V*AC 88…264 / DC 77…286 V*B91065100
IRDH275-427AC 0…793 V / DC 0…650 V*AC 19.2…55 V / DC 19.2…72 VB91065104
IRDH275-425AC 0…793 V / DC 0…650 V*DC 10.2…36 VB91065108
IRDH275B-435AC 0…793 V / DC 0…650 V*AC 88…264 / DC 77…286 V*B91065101
IRDH275B-427AC 0…793 V / DC 0…650 V*AC 19.2…55 V / DC 19.2…72 VB91065105
IRDH275B-425AC 0…793 V / DC 0…650 V*DC 10.2…36 VB91065109
* Absolute values

Downloads for ISOMETER® IRDH275



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