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 All
magnetic locators operate on the same basic principle; two fluxgate
magnetometer sensors, securely mounted inside a rigid sensor support
tube, measure the local magnetic
field.
These
two-magnetometer sensors are vector sensors. Mounted 20” apart,
each measures the average magnetic field component along their
sensitive axis, or the magnetic field component along the
longitudinal axis of the sensor tube.
To work
properly, the magnetometer sensors are aligned opposing so the
magnetic field measured by one sensor is the negative of
 the
magnetic field measured by the other. The locator then sums the
output of the two sensors and cancels any field common to both, such
as the Earth’s Magnetic Field, and leaves only the differential
magnetic field.
The
differential magnetic field, or the magnetic field detected by one
sensor and not the other, is the magnetic field of interest and
hopefully represents the magnetic field of your target and not the
field of your pocketknife, watch or the steel arch support in your
shoes. The drawing on the right shows the construction of a typical
magnetic locator and the location of the two sensing elements.
In the field,
great performance goes hand-in-hand with proper operation. When
searching for survey benchmarks or underground ferrous targets the
magnetic locator should be held in vertically or in a near vertical
position. In this position the instrument audio output is facing
the operator and the controls are readily accessible.
To pinpoint
your target, rotate the instrument to the vertical and use and "X"
or crossing pattern. The audio output will peak directly over your
target. It's that easy!
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