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1.0
INTRODUCTION
The Mag-01(H) magnetometer system is intended for the vectorial analysis of relatively
weak (nT) slowly (10Hz max) varying magnetic fields.
The system comprises one of a range of miniature fluxgate probes connected by a cable to
a compact electronics unit. The electronics unit contains circuitry to convert the signals
produced by the probe into a measurement of flux density for display on the front panel
LCD or in the form of an analog output voltage for chart-recording purposes. A
rechargeable battery is included, making the unit suitable for portable use.
The use of low signature components, including a non-magnetic battery, within the
magnetometers allows the instrument to be used close to the probe. Errors will not be
significant with the probe and magnetometer as close as 0.5 metres.
A precision voltage to current converter maintains precise calibration over the full range
of operating temperatures.
The Mag-01H differs from the Mag-01 due to the addition of a x10 sensitivity control to
increase resolution and the provision of a precision offset control to expand the
measuring range.
Both instruments display the battery voltage for 2 to 4 seconds after switch-on and an
audible alarm signals when the battery should be recharged.
2.0
THE MAGNETOMETERS - See figures 2, 3, 4, 5 and 6
Circuitry
The probe excitation oscillator supplies a high purity alternating signal to the excitation
winding of the Mag probe. The axial component of any magnetic field intercepted by the
probe produces a signal which is filtered to eliminate unwanted noise. Following
detection, an amplified error signal is fed back to the probe via a current converter and
precision wound feedback winding where nulling of the magnetic field occurs. In this
way a precise measurement of field strength is obtained in the form of a voltage which is
fed to the auto-ranging 4½ digit display and analog output socket.
The battery charger, rechargeable battery and voltage regulators power the electronics
unit.
Additional circuitry for Mag-01H
The Mag-01H contains an attenuator which, when selected by the x10 range control
switch, reduces the current feedback to the probe and thereby increases the sensitivity by
a factor of 10.
The Mag-01H also contains a switched precision offset current control which can be used
to back-off field strength values and thereby display or record measurements to the
highest resolution.
OM0382 ISSUE 8 PAGE 3 OF 14
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