• Insulation monitoring device for AC and DC IT systems
  • Application control circuits
  • According to IEC 61557-8
  • Adjustable response value
  • Alarm relay with a potential-free changeover contact

The ISOMETER®s of the IR125Y series are designed to monitor the insulation resistance of unearthed AC and DC control circuits (IT systems). External supply voltage is not required.
In contrast to insulation monitoring devices which evaluate the shift voltage for insulation fault detection, this series uses the active AMP measurement method. This creates the possibility to detect and indicate both symmetrical and asymmetrical insulation faults.

The product has been discontinued

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  • Insulation monitoring for AC and DC systems (IT systems)
  • Response values, adjustable 10…200 kΩ
  • LEDs: Power On LED, alarm LED to signal insulation faults
  • Internal combined test and reset button
  • Connection external reset button
  • Alarm relay with one potential-free changeover contact
  • N/C operation
  • Fault memory behaviour, selectable
  • AC and DC control and auxiliary circuits in accordance with DIN EN 60204-1 "Electrical equipment of machines", IEC 60204-1, EN 60204-1
  • DC auxiliary circuits in accordance with DIN VDE 0100-725
  • Simple battery systems


Optional accessories for ISOMETER® IR125Y-4

TypeArt. No.
Mounting plateB990056

Variants of ISOMETER® IR125Y-4

TypeNominal system voltage UnArt. No.
IR125Y-4AC 19,2…265 V, DC 19,2…308 V*B91023005
*Absolute value

Downloads for ISOMETER® IR125Y-4



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