Magnetic Hysteresis; Environmental Precautions - Bartington Mag690 Operation Manual

b. When the sensor output is digitized, it may be necessary to include an analogue low-pass
anti-alias filter to prevent the creation of in-band noise by beating the 15kHz excitation with
the sampling clock of the digitizer.
The level of unwanted breakthrough at 15kHz has been minimized in the Mag690 but may
still cause an apparently raised noise level when sampled at low sampling frequencies
without further analogue filtering.
c. In applications such as surveillance and magnetic signature monitoring, it may be required
to remove both the DC standing field and all AC noise and pick-up above a set frequency. The
band of interest will be, say, 0.01 to 10Hz, and a band pass filter can be used to provide the
required signal.
The Magmeter and PSU1 power supply units, which can be used with all sensors, contain
three low pass filters with a -3dB point at 4.5kHz together with three high pass filters with a
-3dB point at 0.1Hz.
The SCU1 signal conditioning unit provides filters with independent control of the low and
high pass filter sections, together with offset and gain control for the output of each axis.

5.6. Magnetic Hysteresis

The Mag690 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.

5.7. Environmental Precautions

Refer to the product brochure for maximum environmental electrical and mechanical ratings.
Caution: Exceeding the maximum ratings may cause irreparable damage to your sensor.
BARTINGTON INSTRUMENTS
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