Lightning Protection for Load Cell Installations

Celsum Technologies' Managing Director, Roy Carter, said, The IPU40 system is a welcome addition to our range of instrumentation. Lightning can damage both the load sensors and the conditioning and monitoring instrumentation, and can be a serious danger to personnel, computers and other equipment. As well as a direct hit being an obvious danger, lightning strikes near to the installation can generate transient ground surges, giving high circulating ground currents within cables and equipment. Additionally, electrical currents may be magnetically induced between currents in the cable screens and the inner signal conductors. These can all wreck sensitive electronics, causing at worst death and injury, and at best loss of production and progress as equipment is repaired.

The IPU40 is a pre-wired, tested, load cell integrated protection unit, with cable glands for input and output cables and a sturdy brass earth connection. Housed in a rugged, IP67-rated enclosure, the IPU40 contains three DIN-Rail mounted ZW33 protection barriers with easy-to-wire screw-clamp connections to allow rapid fitting in the field. For full protection, one IPU40 would be fitted close to the load cell, and another close to the instrumentation station. The barriers will accomodate a maximum surge current of 20,000 amps, and typically will clamp voltages to 33V. Line resistance is 3.3 ohms, which is normally calibrated out.