United Kingdom - english


  • 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. -
Available until 31.12.2023.

  • Features
  • Applications
  • Accessories
  • Ordering information
  • Downloads
  • 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 values 1 kΩ…10 MΩ
  • AMPPlus measurement method
  • Automatic adaptation to the system leakage capacitance
  • Info button to display device settings and the system leakage capacitance
  • Continuous self monitoring, with automatic alarm message
  • Automatic self test, selectable
  • Connection for external kΩ indication
  • Test and reset button
  • Connection external test and reset button
  • Two separate alarm relays with two potential-free changeover contacts
  • N/O or N/C operation
  • Alarm relay for system fault (N/C operation)
  • Backlit LC display
  • RS-485 interface
  • Plug-in terminals
  • AC, DC or AC/DC main circuits
  • AC/DC main circuits with directly connected DC components, such as rectifiers, converters, and thyristorcontrolled 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® IRDH375

External kΩ measuring instruments (400 µA)
TypeSKMP *2)Art. No.
7204-1421120 kΩB986763
9604-1421120 kΩB986764
*2) SKMP = scale centre point

External kΩ measuring instrument 20 mA
TypeArt. No.

Transparent front plate cover IP65
TypeArt. No.
144 x 72B98060005

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

Variants of ISOMETER® IRDH375

TypeNominal voltage UnSupply voltage USArt. No.
IRDH375-435AC 0…793 V / DC 0…650 V*AC 88…264 V / DC 77…286 V*B91065000
IRDH375-427AC 0…793 V / DC 0…650 V*DC 19.2…72 V*B91065002
IRDH375B-435AC 0…793 V / DC 0…650 V*AC 88…264 V / DC 77…286 V*B91065004
IRDH375B-427AC 0…793 V / DC 0…650 V*DC 19.2…72 V*B91065006
* absolute values
Device “Option-W” with increased shock and vibration resistance: Indicated by the letter “W” at the end of the order number

Downloads for ISOMETER® IRDH375



Category Product Language Size Download