EMCheck® MWMZ II | EMC - Measuring clamp for equipotential bondings

The EMCheck® MWMZ II is a mesh resistance measuring clamp designed for verifying equipotential bonding quality and shield loop resistance in industrial automation installations. Where straying currents and high-frequency interference from frequency converters find their way onto data cable shields instead of traveling through the intended equipotential bonding system, the root cause is typically inadequate bonding — and the only reliable way to confirm adequate bonding is measurement. The MWMZ II provides that measurement capability without interrupting live circuits, making it practical for use on operating production systems during routine maintenance, commissioning, and acceptance testing. Its measurement method complies with DIN EN 50310, the standard cited in the PROFIBUS & PROFINET International (PI) guideline on functional potential equalization and shielding of PROFIBUS and PROFINET installations.

Key Features
Non-interrupting impedance measurement using a two-coil induction method operating at 2083 Hz. The first coil induces a defined voltage at a defined frequency; the second coil measures the resulting current. The ratio of these values determines the AC resistance (impedance) of the conductor under test — without opening the circuit or interrupting system operation. Measurements can be taken on conductors carrying current during normal operation.

Shield loop resistance measurement for data cables including bus cables and measurement system cables. The MWMZ II provides metrological confirmation that shield loop resistance meets the 0.6 ohm maximum impedance value required for effective shielding, and identifies cables where deteriorating shield connections are increasing loop resistance beyond acceptable limits.

PE and PA loop resistance measurement for equipotential bonding conductors laid pursuant to DIN EN 50310. Loop resistances in the range of approximately 0.3 ohm indicate adequate equipotential bonding; values above this threshold point to bonding deficiencies that allow stray currents to return through cable shields instead of the intended bonding path.

Motor cable shield quality measurement for frequency-controlled drives, including resistance verification of the reverse current path. This application is particularly relevant in facilities with VFDs and servo systems, where inadequate motor cable shielding is a common source of EMC interference affecting nearby fieldbus and industrial Ethernet communication.

Contact voltage detection with automatic alert when a dangerous voltage level is detected on the conductor under test. This safety feature protects technicians during measurement activities in environments where unexpected voltages may be present on bonding conductors or cable shields.

Up to 300 measurements with integrated time stamp recording for documentation purposes. Stored readings support acceptance testing documentation, baseline comparisons over time, and compliance verification against applicable standards.

OLED display with a 48 mm x 39 mm active surface for clear readability of measurement values, timestamps, and alert indicators in all lighting conditions typical of industrial environments.

Common Applications
EMC commissioning and acceptance testing on new PROFIBUS, PROFINET, and industrial Ethernet installations, providing documented proof that equipotential bonding and cable shielding meet the requirements of DIN EN 50310 before the system enters production.

Troubleshooting intermittent fieldbus errors and EMC-related communication disruptions where the interference source is suspected to be inadequate equipotential bonding or deteriorating shield connections rather than bus hardware or configuration issues.

Routine maintenance verification in facilities with high electromagnetic noise sources — including variable frequency drives, servo systems, welding equipment, and large motors — where bonding quality can degrade over time due to corrosion, loose connections, or conductor damage.

System integrator and machine builder use for verifying and documenting the EMC conformity of completed installations prior to customer handover, providing measurable evidence that the installation meets applicable standards.

Paired use with the EMCheck® LSMZ I leakage current clamp for complete EMC installation verification — the MWMZ II confirms bonding and shield resistance quality while the LSMZ I confirms that shield current levels are within acceptable limits.

Technical Specifications
-Measurement method: Two-coil induction, non-interrupting, at 2083 Hz
-Measures: Earth loop resistance, earth loop inductivity, contact voltage
-Shield loop resistance guideline: Max. 0.6 ohm
-PE/PA loop resistance guideline: Max. approx. 0.3 ohm
-Data storage: Up to 300 measurements with time stamp
-Display: OLED, 48 mm x 39 mm active surface
-Safety feature: Contact voltage alert
-Standard compliance: DIN EN 50310

The EMCheck® MWMZ II delivers the metrological proof that equipotential bonding and shielding quality meet defined standards — turning assumption-based assessments of EMC installation quality into documented, measurement-backed verification.

Learn more here: https://indusolamerica.com/emc/emcheck-mwmz-ii-emc-measuring-clamp-for-equipotential-bondings-122010010/