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ISOMETER® isoHV425 mit AGH422

ISOMETER® isoHV425 with AGH422

  • Continuous insulation monitoring at a nominal system voltage of AC/DC 0 V … 1000 V
  • Galvanically separated interface allows predictive maintenance of the system being monitored
  • Measurement of nominal system voltages and partial voltages to earth
  • Automatic adjustment to the system leakage capacitance up to 150 µF
  • Indication of the insulation value distribution (conductors L1/+ and L2/-) in DC systems

The ISOMETER® monitors the insulation resistance of unearthed AC, AC/DC and DC systems (IT systems) with nominal system voltages of 3(N)AC, AC/DC 0 … 1000 V or DC 0 …1000 V. The maximum permissible system leakage capacitance Ce is 150 μF. DC components existing in AC systems do not influence the operating characteristics, when a minimum load current of DC 100 mA flows. A separate supply voltage allows de-energised systems to be monitored too.

In order to meet the requirements of applicable standards, customised parameter settings must be made on the equipment in order to adapt it to local equipment and operating conditions. Please heed the limits of the area of application indicated in the technical specifications. Any use other than that described in this manual is regarded as improper.


  • Monitoring the insulation resistance for unearthed AC/DC systems
  • Measurement of the mains voltage (true r.m.s.) with undervoltage and overvoltage detection
  • Measurement of DC system voltages to earth (L1+/PE and L2-/PE)
  • Automatic adaptation to the system leakage capacitance up to 150 μF
  • Selectable start-up delay, response delay and delay on release
  • Two separately adjustable response value ranges of 10...500 kΩ (Alarm 1, Alarm 2)
  • Alarm signalling via LEDs (AL1, AL2), a display and alarm relays (K1, K2)
  • Automatic device self test with connection monitoring
  • Selectable N/C or N/O relay operation
  • Measured value indication via a multifunctional LC display
  • Fault memory can be activated
  • Password protection to prevent unauthorised parameter changes


  • RS-485 (galvanically separated) including the following protocols:
    – BMS interface (Bender measuring device interface) for data exchange with other Bender components
    – Modbus RTU
    – IsoData (for continuous data output)


  • 0…10 V analogue output (galvanically separated)


  • AC main circuits up to 1000 V
  • DC main circuits up to 1000 V
  • Systems including switched-mode power supplies

ISOMETER® isoHV425 with AGH422 Variant(s)

TypeSupply voltage USNominal voltage UnVersionArt.-Nr.
isoHV425-D4-4 with AGH422AC 100…240 V, 47…63 Hz/DC 24…240 VAC-, 3(N)AC, DC 0…1000 VSerial interfaceB71036501
isoHV425W-D4-4 with AGH422WAC 100…240 V, 47…63 Hz/DC 24…240 VAC-, 3(N)AC, DC 0…1000 VSerial interfaceB71036501W
isoHV425-D4M-4 with AGH422AC 100…240 V, 47…63 Hz/DC 24…240 VAC-, 3(N)AC, DC 0…1000 VAnalogue outputB71036503
isoHV425W-D4M-4 with AGH422WAC 100…240 V, 47…63 Hz/DC 24…240 VAC-, 3(N)AC, DC 0…1000 VAnalogue outputB71036503W

Optional Accessories for ISOMETER® isoHV425 with AGH422

TypeArt. No.
Mounting clip for screw mounting (one piece per device)B98060008
Mounting frame XM420B990994 

Downloads for ISOMETER® isoHV425 with AGH422

Certificates TÜV NORD - isoHV42x, AGH42x, isoHV52x, isoRW42x und VMx420 431.9 KB DE2023/01/12 14:46:3012.01.2023 14:46:30
Certificates TÜV NORD - isoHV42x, AGH42x, isoHV52x, isoRW42x and VMx420 411.7 KB EN2023/01/12 14:46:3512.01.2023 14:46:35
CE Declarations of conformity isoXX425 151.9 KB 2023/01/09 06:50:5109.01.2023 06:50:51
Manuals isoHV425 3.1 MB DE2021/09/14 11:52:1314.09.2021 11:52:13D00082
Manuals isoHV425 3.1 MB EN2021/09/14 08:33:5114.09.2021 08:33:51D00082
Quickstarts isoHV425 1.0 MB DE2021/07/30 09:11:1230.07.2021 09:11:12D00082
Quickstarts isoHV425 1.0 MB EN2021/07/30 09:11:1230.07.2021 09:11:12D00082
Manuals isoHV425 1.4 MB FR2019/05/13 10:31:5513.05.2019 10:31:55D00082
Datasheets isoHV425 477.4 KB DE2022/05/25 07:07:0225.05.2022 07:07:02D00082
Datasheets isoHV425 474.3 KB EN2022/06/09 10:54:3809.06.2022 10:54:38D00082
Software Modbus RTU - Monitor isoxx425 V2.2.2 setup 7.1 MB 2019/05/13 10:31:5913.05.2019 10:31:59
Datasheets isoHV425 477.0 KB FR2022/06/09 10:55:1509.06.2022 10:55:15D00082
Datasheets isoHV425 476.4 KB ES2022/06/09 10:55:5209.06.2022 10:55:52D00082