Item # 122010005 – EMCheck LSMZ I | EMC – Measuring clamp for leakage current 
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Measuring and avoiding shield currents

Often in industrial data communication, the reason for sporadic disturbances is caused by high-frequency shield currents. By measuring the compensating currents over the data line shield, it becomes clear that the Fieldbus itself is not the reason for failure problems. It is critical to find out what caused the failure and take countermeasures.

The EMCheck® LSMZ I leakage current clamp is specially designed for measuring low and high-frequency leakage and shield currents in the 50/60 kHz or 5 Hz – 1kHz frequency range. The adjustable measuring range is possible in levels from 30 μA – 100 A, whereby the lower range is of particular interest for measuring the shield current of the data cable.

    The EMCheck® LSMZ I features a large jaw opening, 2.8 cm, so that the cable can easily pass-through for convenient, comfortable measurements even in unfavorable installation situations. It is possible to perform permanent measurements, such as maximum currents, by using the hold function.

    Based on our experiences at Indu-Sol, a shield current of <40mA has proven to be adequate regardless of the machine specifications. In the case of larger shield and leakage currents, additional actions have to take place to improve the equipotential bonding or eliminate the source of interference.

    The official value for the maximum electrical conductivity of a screen is 150 mA, and anything beyond that will lead to a decrease in the shielding effect and electrical overload of the devices. The limit value for equipotential bonding conductors is (for touch protection reasons) at 300 mA. Protective conductors routed within a cable may carry a maximum of 5% of the flowing phase current.