Improved high bandwidth potential-free magnetic field probe

An improved potential-free sensor for the measurement of magnetic fields is presented. The inductive sensor has a frequency range from 30 Hz up to 300 MHz (3 dB-cutoff-frequencies). The high bandwidth is achieved due to modern high frequency telecommunication ICs and laser diodes for the transmission of the analog magnetic field signals via a fibre optic link to the receiver unit. The sensor allows the potential-free measurement of magnetic fields in the region of high voltage equipment. Even very fast transient magnetic fields caused by NEMP, ESD, LEMP or SF₆ circuit breaker operations in HV switchgear can be measured. Compared to other field probes the dynamic range has been increased significantly. The range of the magnetic fields that can be measured reaches from 0.8 A/m to 1500 A/m which is equivalent to a dynamic range of more than 65 dB. The handling and calibration of the new field probe has been improved using a RISC-microcontroller in both the sensor and the receiver systems. Thus all measurement functions and also battery power management can be controlled very flexibly. The maximum continuous operating time limited by the battery is about three hours