There are several methods used by underground cable locating services, the electromagnetic being the most common. Using the right frequency is essential in this case, so the operator must have basic knowledge of the signal properties, in order to be able to select the optimal frequency.
But what is frequency?
Frequency results from the number of times per second that the magnetic field builds and collapses. It is measured in hertz (Hz). Radio frequency receivers are instruments able to detect cables radiating their own electromagnetic field and the most common technique in electromagnetic location consists in utilizing an output lead connected to the target facility and a ground lead attached to a grounding point.
How to choose the right frequency for cable locating?
Choosing the adequate frequency depends on some factors, such as ground conditions or line conductivity. Typically, technicians use the lowest frequency that gives a traceable signal over a certain distance.
Types of frequency
- Very low to low (128 Hz – 1 kHz)
- Medium (4 – 40 kH z)
- High (40 – 300 kHz)
- Very-high (>300 kHz)
Using the right frequency for underground cable locating services can be done by taking into consideration the resistance of the circuit and the goal of the locating process.
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