The is a 3-axis AC magnetic field sensor was developed at Spicer Consulting for the SC24 generation of field cancelling systems. It has lower noise levels and a faster overload recovery than the previous model. Use this sensor and an SC22 or SC24 control unit to stop beam disturbances due to AC line fields. The sensor contains 3 orthogonal coils. The built-in electronics integrates and amplifies the coil signal to provide a measurement of magnetic flux density. The bandwidth of the sensor is optimized for very low 1/f noise. This means that when used with a magnetic field cancelling system, it generates negligible low-frequency magnetic field. The sensor recovers quickly after an overload caused by large step changes in the DC field generated by the microscope. These occur during TEM magnification changes or operating mode changes of dual beam systems.