MRI system is a high-precision imaging diagnostic equipment, which has high requirements for the installation environment. The NMR signal is a very weak signal, which is susceptible to external interference. As a result, MRI systems often need to be equipped with Faraday cages (shielding rooms) to isolate external RF interference from entering the system. However, the Faraday cage has better attenuation for the radio frequency band, and the shielding effect for the low frequency is relatively limited. Especially for the installation of MRI systems near subways, trains, large transformers, elevators, power transmission cables, etc. Not only must the Faraday cage be configured, but also the active shielding system must be configured to make the MRI system meet the diagnostic requirements.

CSJ-ASH is a high-performance low-frequency electromagnetic field active shielding system developed by Ningbo Chuanshan Jia Electromechanical Co., Ltd. It can effectively shield DC electromagnetic fields, 50Hz/60Hz power frequency electromagnetic fields caused by subways, trains, trams, transmission cables, transformer equipment, elevators, etc. CSJ-ASH consists of three major components: fluxgate high-precision probe, host, and shielding coil. The high-precision fluxgate probe can sense the environmental electromagnetic field interference, and generate the corresponding electrical signal to transmit to the host. After processing, the host outputs a reverse current that follows in real time, and the current generates a reverse magnetic field in the shielding coil to cancel the interference magnetic field, thereby realizing active shielding of low-frequency electromagnetic fields.