The performance and capabilities of magnetometers are described through their technical specifications. Major specifications include
*Sample rate is the number of readings given per second. The inverse is the cycle time in seconds per reading. Sample rate is important in mobile magnetometers; the sample rate and the vehicle speed determine the distance between measurements.
*Bandwidth or bandpass characterizes how well a magnetometer tracks rapid changes in magnetic field. For magnetometers with no onboard signal processing, bandwidth is determined by the Nyquist limit set by sample rate. Modern magnetometers may perform smoothing or averaging over sequential samples, achieving a lower noise in exchange for lower bandwidth.
*Resolution is the smallest change in a magnetic field the magnetometer can resolve. A magnetometer should have a resolution a good deal smaller than the smallest change one wishes to observe. This includes quantization error which is caused by recording roundoff and truncation of digital expressions of the data.
*Absolute error is the difference between the readings of a magnetometer true magnetic field.
*Drift is the change in absolute error over time.
*Thermal stability is the dependence of the measurement on temperature. It is given as a temperature coefficient in units of nT per degree Celsius.
*Noise is the random fluctuations generated by the magnetometer sensor or electronics. Noise is given in units of , where frequency component refers to the bandwidth.
*Sensitivity is the larger of the noise or the resolution.
*Heading error is the change in the measurement due to a change in orientation of the instrument in a constant magnetic field.
*The dead zone is the angular region of magnetometer orientation in which the instrument produces poor or no measurements. All optically pumped, proton-free precession, and Overhauser magnetometers experience some dead zone effects.
*Gradient tolerance is the ability of a magnetometer to obtain a reliable measurement in the presence of a magnetic field gradient. In surveys of unexploded ordnance or landfills, gradients can be large.