Specifications

BARTINGTON INSTRUMENTS
Page 8 of 12 M2240 ISSUE 1
Performance
Signal Processing
For different applications it may be necessary to process the signal from the sensor in different ways:
In order to increase the sensitivity of the recording system it may be necessary to back-off the earth’s field
and amplify only the changes in the field from the current value. This requires a high-pass filter, which
could be a simple capacitively coupled arrangement or a multi-pole filter to provide a steep roll off
characteristic. These features are all present in the SCU1 signal conditioning unit.
The output from all fluxgate sensors will contain noise from the driving electronics. For the Mag639 this
noise is at 32kHz which is well above the bandwidth of the sensors. Where low noise operation is required
a filter should always be provided to reject the noise which lies outside the band of interest.
When the sensor output is digitized it may be necessary to include an analog low-pass anti-alias filter to
prevent the creation of in-band noise by beating the 32kHz excitation with the sampling clock of the
digitizer.
The level of unwanted breakthrough at 32kHz has been minimized in the Mag639 but may still cause an
apparently raised noise level when sampled at low sampling frequencies without further analog filtering.
Magnetic Hysteresis
The Mag639 is designed to have an extremely low magnetic hysteresis. However, Bartington Instruments
recommends your magnetometer is not subjected to magnetic fields greater than their stated measuring
range for extended periods as this could alter the DC offset. If this occurs, the offset will exhibit drift as it
returns to its original offset specification.
Caution: Subjecting the magnetometer to fields in excess of 2 x the nominal range may cause
inaccuracy in future measurements. Degaussing the magnetometer can reverse such an effect.
Environmental Precautions
Refer to the datasheet for maximum environmental electrical and mechanical ratings.
Caution: Exceeding the maximum ratings may cause irreparable damage to your sensor.