GMW BARTINGTON MAG-03, Руководство по эксплуатации

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OM1004 ISSUE 20 PAGE 14 OF 30
The output from all fluxgate sensors will contain noise from the driving electronics. For the
Mag -03 range this noise is at 15kHz 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.
The Mag -03PSU power supply unit, which can be used with all sensors, contains 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 Mag -03DAM data acquisition module contains anti-aliasing filters which are software
controlled. The high resolution of this unit allows small changes to be recorded even in the
presence of the earth’s field.
The Mag -03SCU 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.
9 CARE AND MAINTENANCE
The Mag -03 sensor contains no user-serviceable parts but, provided it is operated within the
design limits, it will require no attention for many years. Surface or dirt contamination
should be removed using a mild detergent solution only. If the connector pins become
contaminated they should be lightly cleaned with a swab of isopropyl alcohol.
The unit must be returned to Bartington Instruments for repair or re-calibration. For the
diagnosis of faults within the unit special equipment is required including a zero gauss
shielded chamber, a calibrated test coil with traceable calibration, and a.c. and d.c. calibrated
constant current sources. Much of this equipment is beyond the scope of normal service
facilities. Any field tests are therefore limited to those which can detect if the magnetic field
sensor and associated circuitry does not produce an analog voltage which is proportional to
the magnetic flux.
If each sensor element in turn is rotated planar to the terrestrial magnetic field, a sinusoidal
analog output should be produced at the relevant output. If this is not the case, or a gross
asymmetry is seen in the output, then a fault clearly exists.
The frequency response of individual channels can be tested by comparing the analog outputs
from each channel using an oscilloscope. If each axis is aligned in turn close to equipment
containing a mains transformer, the stray fields will contain 2nd and 3rd harmonics of the
mains frequency and each channel should give identical results. This will give a rough check
on the operation of each channel to a few hundred Hz.
10 MAGNETIC UNITS AND MEASUREMENTS
10.1 CONVENTIONS
The Mag -03MC analog output is positive for conventional flux direction South to North in
the direction of the arrow given for each axis. The measurement axes are designated X, Y
and Z in the Cartesian co-ordinate system when viewed from the top or non-connector end of
the sensor.