How to automate insulation resistance testing? Integration of Sonel MIC-RS meters into production systems
The requirement to implement repeatable and automated insulation resistance testing directly on production lines has driven the design and development of dedicated measuring instruments. Sonel MIC-RS meters address this requirement by combining measurement capabilities with a design typical of industrial automation components: DIN rail mounting (using external adapters), an isolated 24 V DC power supply and full compliance with industrial standards (including EN IEC 61557, EN 61010 and EMC requirements for industrial environments).
Key measurement parameters and operating modes
From a technical standpoint, the MIC-RS series offers the range of test voltages required by applicable standards:
- Sonel MIC-RS: up to 1 kV,
- Sonel MIC-RS2: up to 2.5 kV,
- Sonel MIC-RS3: up to 5 kV.
In addition, the instruments support stepwise voltage adjustment while maintaining nominal test currents of ISC ≤ 2 mA, in compliance with EN IEC 61557-2. The available operating modes – insulation resistance measurement (RISO), measurement with continuously increasing voltage (RampTest) and post-RISO capacitance measurement (MIC-RS only) allow the test procedure to be tailored to the characteristics of the tested object.
Image 1. Sonel MIC-RS series insulation resistance meters
Specific aspects of implementation in PLC/SCADA systems (Modbus RTU)
From an automation engineer’s perspective, the communication interface is a key consideration. The devices communicate via the Modbus RTU protocol, with system integration based on register map management. Such an architecture simplifies the implementation of function blocks (FBs) in PLC controllers (e.g. Siemens S7, Rockwell) and enables direct mapping of variables (tags) to SCADA/HMI systems.
Control logic and machine safety
The meters operate exclusively as slave devices, with all actions, including test initiation and parameter changes, triggered by the master system. Built-in status flags (for MIC-RS2 and MIC-RS3: hv – high voltage, noise – interference, limit – limit exceeded, udet – voltage detected, ready – ready status) are essential for implementing interlock logic within the PLC. They allow the process to be immediately stopped (for example, by disabling the test voltage) if insulation breakdown, excessive leakage current or voltage on the tested object is detected. Key safety functions also include automatic discharge of the tested object after completion of the test and protection of measuring inputs against external voltage, ensuring the safety of both the workstation and personnel.
Application areas
The meters are designed for integration into electrical component testing lines and quality control stations, including End-of-Line testing. Typical application environments include:
- switchboard and control cabinet manufacturing (testing of circuits and busbar insulation),
- domestic appliance and electronics manufacturing (power modules, power supplies, high-voltage sections),
- plastics processing (validation of insulation for heaters as well as power and control wiring harnesses),
- rail rolling stock and automotive industries (components and wiring systems).
Deployments such as e²Tango systems (medium-voltage switchgear testing) or manufacturing of insulation components demonstrate the suitability of the devices for both end-of-line and in-process testing.
Image 2. Sonel MIC-RS2 as an integral element the production process in an industrial facility
Support for design processes (CAD/CAE)
Sonel MIC-RS series meters provide flexible adaptation of communication protocols, simplifying integration in facilities with non-standard network standards. Detailed information and tailored communication protocol adaptations are available directly from the manufacturer.
Looking ahead, the meters could be incorporated into engineering design libraries. Ready-to-use macros and symbols for systems such as EPLAN, SEE Electrical, AutoCAD Electrical or IGE+XAO would significantly reduce control cabinet design time and accelerate BOM generation by eliminating the need for manual measurement block definition within schematic diagrams.
Technical conclusions for the system integrator
For automation system integrators, the MIC-RS meter series represents a dedicated, industrial-grade solution for insulation resistance testing, combining measurement and control functionality Full process control via the Modbus protocol (including access to status flags and RISO/RampTest results) and an industrial-grade design (DIN rail mounting, 24 V DC power supply) significantly reduce commissioning time. The deployment of this type of meters eliminates variability associated with manual measurements and ensures fully deterministic acquisition and recording of quality data for each tested product, with seamless integration into existing control infrastructures such as PLC and SCADA systems.
Image 3. Practical example of the Sonel MIC-RS2 installed in the connection compartment of a medium-voltage switchgear panel
Detailed specifications of Sonel MIC-RS series meters are available on the product pages online.
Author:
Wojciech Siergiej, Sonel S.A.
