By sending a 1 kHz electromagnetic wave signal to the underground cable through the transmitter, the cable locator probe is used to measure the direction and depth of the cable based on the principle that when the probe is perpendicular to the magnetic field lines on the ground plane, the received signal is minimal (almost zero). When the probe moves parallel to the ground plane and the signal sound suddenly becomes weaker, that indicates the open circuit point and short circuit point of the cable.
1. Zero-value method (minimum method): Hold the probe perpendicular to the ground. When directly above the cable, the received signal is minimal (the meter reading is the smallest). This detection method is called the zero-value method.
2. Peak method (maximum method): Hold the probe parallel to the ground and perpendicular to the cable direction. When directly above the cable, the received signal is the strongest (the meter reading is the maximum). This detection method is called the peak method.
3. Depth detection: The principle of measuring burial depth is as follows: first, hold the probe perpendicular to the ground to find point A directly above the cable (mark this point), then tilt the probe at a 45-degree angle to the ground, keeping it close to the ground and perpendicular to the cable direction, and move it to one side until you find the position B with the weakest sound. From the figure, the cable center is O, so triangle ABO is an isosceles right triangle, thus AB = AO, which is the burial depth.
By sending a 1 kHz electromagnetic wave signal to the underground cable through the transmitter, when a fault occurs in the underground cable and breaks down, the core wire comes into contact with the earth lead sheath; if an AC signal is applied to this core wire or lead sheath, a current loop is formed at the fault point, generating a leakage signal that radiates to the ground, creating a leakage electric field in the earth. The radiation signal is strongest directly above the leak point. Using the two probes of the A-frame to pick up this gradient signal, by moving the A-frame, the strongest point of the leak signal can be found. Based on this principle, the fault point of the underground cable can be accurately located.
