MADS hardware

The MADS system consists of two high-speed digital fluxgate APS 540* magnetometers. With a sample rate of 250 times/sec, the Nyquist theorem dictates that the maximum frequency detectable is 125 Hz. A filter has been fitted permanently in the sensors to block frequencies above this value and avoid problems with aliasing. The digital sensors are connected, via RS232 cables, to separate Dell laptop computers.

540 Sensor specification

Accuracy ±1% FS
Noise level ±0.5 nT
Range ±100 μT
Scale stability ±.05% FS/°C
Initial offset < ±200 nT
Offset vs. temp < 5nT/°C
Orthogonality of axes better than ±0.2°
Alignment of axes with package better than ±0.2°
Linearity ±0.1% full scale
Maximum data transfer 250 3-axis samples/sec

* Though the 540 is no longer manufactured, the 539 model has a very similar specification.