Description

Theory of Operation: 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.
The two-magnetometer sensors are vector sensors, mounted 20″ apart and each measures the average magnetic field component along their sensitive axis, i.e. the magnetic field component along the longitudinal axis of the sensor tube.
For a magnetic locator to work properly, the magnetometer sensors are aligned opposing so that 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. By summing the two output signals, you cancel any field common to both sensors, such as the Earth’s Magnetic Field, and leave only the differential magnetic field.
The differential magnetic field, 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 left shows the construction of a typical magnetic locator and the location of the two sensing elements.

Field Operation: Good instrument performance goes hand-in-hand with proper operation. When searching for survey benchmarks or underground ferrous targets, the magnetic locator should be held in the vertical or near vertical position. In this position the instrument audio output is facing the operator and the controls are readily accessible. The picture at the top of this page shows how to hold the instrument for optimum operation.
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.