Insulation monitoring unit
Microsite Electronics
Insulation monitoring unit

Insulation monitoring unit (IMU)

As hybrid and electric vehicles gain in importance, batteries must be able to store electrical energy and provide sufficient quantities of energy to operate the electric drives.

The insulation monitoring unit monitors the insulation resistance of the high voltage vehicle electrical system and provides effective protection against electric shock.

As a partner for the development of the new insulation monitor, HELLA was able to engage Bender, a company that has been working on electrical insulation monitoring systems for over 65 years and is generally considered to be the world leader in this field.



Insulation monitoring unit
Power consumption < 150 mA in operating mode (ignition on) < 150 μA in standby mode (ignition off)
Insulation resistance measuring accuracy +0/-30 % in measuring range 50 k to 10 Mohm
High voltage measuring accuracy ± 10% at UHV > 100 V ± 5% at UHV > 200 V
Operating temperature - 40 °C to +85 °C
Standard IEC 61557-8, ISO 6469-3
Insulation coordination According to ICE 60664-1 and ICE 60664-3, operating voltage up to 1000 V voltage pulse 6 kV contamination level 2 max. operating height 5000 m
Voltage insulation strength 3 kV according to ISO 6469-3 or ISO 23273
Insulation resistance Min. 100 Ω/V



  • Joint development with BENDER GmbH, the leading supplier of Insulation Monitoring Devices in industry applications
  • Different variants for integration in existing Battery Management Units
  • Standalone modules with CAN interface for an independent use