Innovative technologies for safe handling of electrical power to achieve high availability

We offer you first-class quality and safety combined with global service and every support in resolving your monitoring problems.

  • Electrical safety for unearthed power supplies (IT systems)
  • Insulation monitoring equipment, insulation fault location systems
  • Power supplies for medical applications
  • Measuring and monitoring relays
  • Electrical safety for earthed power supplies (TN systems)
  • Using renewable energies efficiently: wind power, photovoltaics
  • Test systems for electrical equipment and medical technology


  • 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

- This device series is in the discontinuation phase. -
Deliverable according to availability until  31.12.2023.


  • 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

Downloads for ISOMETER® IRDH275

Handbücher IRDH275/IRDH275B 1.4 MB DE13.05.2019 10:31:41D00176
Handbücher IRDH275/IRDH275B 1.4 MB EN13.05.2019 10:31:49D00176
Handbücher IRDH275/IRDH275B 601.5 KB ES13.05.2019 10:31:54D00176
Handbücher IRDH275/IRDH275B 1.4 MB FR13.05.2019 10:31:54D00176
Datenblätter IRDH275 422.5 KB DE14.06.2022 09:08:00D00122
Datenblätter IRDH275 396.8 KB EN14.06.2022 09:08:29D00122

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

ISOMETER® IRDH275 Variants

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