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ISOMETER® iso685…

ISOMETER® iso685 Series

  • Ground-fault monitoring device that measures insulation resistance in ungrounded AC and DC systems, including systems with adjustable-speed drives and power conversion equipment
  • Minimizes unplanned outages and eliminates the need to interrupt power to identify faulted circuits
  • Proactively plan system maintenance by trending insulation deterioration over time
  • Eliminates labor-intensive fault location procedures by identifying faulted circuits automatically when paired with a Bender EDS

The iso685 is the latest generation ground-fault detector for ungrounded AC and DC systems, as well as systems with power conversion equipment such as variable frequency drives and inverters. Using the latest in monitoring technology, the iso685 provides accurate insulation resistance readings on virtually all types of power systems and control systems, with simple installation, setup, and operational features. This device meets or exceeds the requirements of NEC 250.21(B), NEC 250.167(A), and CEC 10-400 for ground detectors in ungrounded systems.

The iso685 connects directly to systems up to 690 VAC or 1000 VDC, and up to 12 kV with optional accessories. Insulation resistance is continuously monitored, allowing for detection and trending of developing ground faults before leakage current may be present. Predefined profiles simplify initial setup and tailor settings to application-specific requirements. Measured values are displayed in real-time on the device's display and via standard Modbus and web server communications.


  • Ground-fault detector for ungrounded single-phase AC, three-phase AC, and DC systems
  • Meets or exceeds code requirements for ground-fault detection on ungrounded systems, including NEC 250.21(B), NEC 250.167(A), and CEC 10-106(2)
  • Works with mixed AC/DC systems, including systems with power conversion equipment such as variable frequency drives and inverters
  • Monitors for ground faults by measuring the system's insulation resistance, allowing for early indication and trending of developing faults before leakage current may be present
  • Two separately adjustable insulation resistance values from 1 kΩ to 10 MΩ
  • Incorporates multiple measurement principles to ensure optimal accuracy on virtually any system type
  • Predefined system profiles simplify setup and tailor operational settings to specific applications
  • Easy-to-use, on-board menu for managing settings
  • Advanced system trending via on-board, time-based graphing
  • A variety of outputs, including relay contacts and analog outputs
  • Built-in web server allows for viewing device status in real-time from any connected PC or mobile device
  • Native Modbus/TCP slave capability
  • Additional option for external, panel-mount HMI
  • Additional option for tiebreaker support - ensure all systems remain monitored regardless of tiebreaker status
  • Additional option for fault location - locate ground faults quickly and automatically when combining the iso685 with EDS440 series fault location modules
  • ANSI 64 ground detector relay
  • Relay outputs, built-in web server, and built-in Modbus/TCP support
  • Additional options for external panel-mount HMI, tiebreaker support, and fault location (when combined with additional equipment)


  • General-purpose ground-fault detection for power distribution per code requirements including NEC 250.21(B), NEC 250.167(A), and CEC 10-106(2)
  • DC and mixed AC/DC systems
  • Systems with power conversion equipment, including variable frequency drives and inverters
  • Large power distribution networks requiring fast ground-fault location
  • Battery backup systems
  • Ships

ISOMETER® iso685 Series Variant(s)

Part No.Built-in DisplayPanel-mount HMITiebreaker SupportFault Location CompatibleOrdering No.

All models are available with additional climate and mechanical protection. Refer to datasheet for more information.

Optional Accessories for ISOMETER® iso685 Series

Voltage couplers for extending supported system voltage range

Part No.Extends Voltage Range ToOrdering No.
AGH150W-4Up to 1150 VAC / 1760 VDCB98018006
AGH204S-4Up to 1650 VAC-1ph / 1300 VAC-3phB914013
AGH520SUp to 7200 VACB913033
AGH676S-4Up to 12 kVACB913055

Downloads for ISOMETER® iso685 Series

Certificates TÜV NORD - isox685x und FP200x 449.0 KB DE2023/01/12 14:43:2912.01.2023 14:43:29
Certificates TÜV NORD - isox685x and FP200x 443.4 KB EN2023/01/12 14:43:3712.01.2023 14:43:37
Datasheets FP200 420.1 KB EN2019/05/13 10:31:3513.05.2019 10:31:35D00179
CE Declarations of Conformity FP200 82.4 KB 2022/08/12 06:17:2412.08.2022 06:17:24
CE Declarations of Conformity iso685 92.3 KB 2022/08/12 06:17:2512.08.2022 06:17:25
Product Brochures iso685 1.8 MB EN2019/05/13 10:31:0113.05.2019 10:31:01D00022
Quickstarts iso685-… 2.5 MB EN2021/03/02 13:36:1902.03.2021 13:36:19D00022
Manuals iso685-… Modbus settings 844.0 KB EN2021/08/25 07:16:4225.08.2021 07:16:42D00022
Manuals iso685-x 10.9 MB EN2022/06/09 10:48:2409.06.2022 10:48:24D00022
Quickstarts FP200 3.2 MB EN2021/06/28 04:56:3228.06.2021 04:56:32D00179
Datasheets iso685-x 1.8 MB EN2021/07/13 13:07:3213.07.2021 13:07:32D00022
Manuals iso685-… web server 560.5 KB EN2019/05/13 10:31:5313.05.2019 10:31:53D00022
Manuals Commissioning iso685-S… devices without a connected Display FP200(W) 1.4 MB EN2021/06/10 12:48:1210.06.2021 12:48:12D00022
Software iso685(W)-S/D Update V1.29 6.2 MB 2021/11/17 05:58:5017.11.2021 05:58:50