• Monitors insulation resistance for unearthed AC control circuits (0-300 V).
• Two adjustable response values with preset function for automatic parameter setting.
• Includes connection monitoring, LEDs for power and alarms, and test/reset buttons.
• Equipped with two alarm relays, selectable N/O or N/C operation, and fault memory.
• Features a multi-functional LC display and adjustable response delay.
• Complies with RoHS standards and uses push-wire terminals.

The ISOMETER® IR420 is designed to monitor insulation resistance in unearthed AC control circuits, particularly in industrial and mechanical engineering applications. It can also monitor de-energised systems using an external supply voltage.

• Suitable for AC control circuits in industrial sectors, power plants, elevators, and automation systems.
• Complies with standards such as DIN EN 60204-1 and DIN VDE 0100-725.

The device displays the current insulation resistance and triggers alarms if resistance falls below preset values. It features two alarm relays for prewarning and alarm distinction. Fault memory retains alarm state until reset.

Automatically checks connections every 24 hours or upon pressing the test button. Displays error codes for connection faults.

Automatically sets response values based on measured nominal system voltage upon initial connection.

Uses superimposed DC voltage for measurement.

Complies with DIN EN 61557-8, EN 61557-8, IEC 61557-8, and ASTM F 1207M-96 (2007).

• Rated insulation voltage: 250 V, impulse voltage: 4 kV.
• Supply voltage options: AC 16-72 V/DC 9.6-94 V or AC/DC 70-300 V.
• Response values adjustable between 1-200 kΩ.
• Operating temperature range: -25 to +55 °C.
• Connection types include screw-type and push-wire terminals.

Available in two models with different supply voltage ranges and terminal types.