Everything You Need to Know about Underground Cable Locators

If you’re planning any large-scale outdoor renovations to your home, like installing an inground pool or connecting to gas lines, you need to be aware that there’s a lot buried underground that may be an unexpected obstacle. Power cables are installed well below ground in most suburbs fresh off the developers’ blueprints, as are NBN lines. In addition, you’ll come by sewage and water pipes. To avoid damage and possible accidents, homeowners need to know the precise location of each. Different tools help in this aspect. For cables, it’s an underground cable locator that can find any piece of wiring connected to your home.

An underground cable locator is a specialised instrument used in locating cables. It will pinpoint where cables are and also detect if a line is broken. They are often used in new projects that require excavation, so no unintentional damage occurs.

Passive vs Active Cable Locators

Underground cable locators read the signals sent from energised lines. Cables in working order will have their own current that is easily picked up by a receiver in the locator. Issues occur in broken lines, with no power present. In this context, there are two basic types of cable locators: passive and active. Passive cable locators can only detect operational cables, whereas active locators can detect these in addition to any faults in severed lines. They do this by energising any cable with a signal induced by a separate transmitter. These signals can be modified to pinpoint the location, and also the type of cable. Active locators provide better precision in location and help in identifying cables. Passive locators, on the other hand, will be enough to locate any operational power cables so as not to cause any damage.

Man working with Cable Locator
Source: radiodetection.com

Features that Make a Difference


Transmitters help increase the strength of the signals so cables that are buried deeper underground won’t be a problem. Transmitters use three modes of operation – direct connect, allowing users to physically connect the transmitter to the cable being located; with a signal clamp, or with spill induction without any connections. Transmitters can emit continuous or pulsed signals for easier and quicker cable detection.

Holding a Transmitters cable locator
Source: youtube.com

Receivers and Displays

Professional grade locators have receivers made of reinforced plastics and IP54 rating, meaning they can be used in any type of weather. A high-definition graphical display presents detailed information of the findings in the form of a map, with helpful features that effectively guide you to the buried cable. When located, the display shows the current of the cable, the direction and the depth.

Holding cable locator with display
Source: youtube.com

Signal Clamps

Transmitter signal clamps induce a current onto the cable. They are used when it is not possible or unsafe to make a physical connection to the core of a target cable, like power lines and telephony lines. Most active locators come with a 100mm signal clamp.

cable locator with Signal Clamps
Source: youtube.com

Variable Frequencies

The simplest and cheapest locators are passive locators with one set frequency. More complicated units with included transmitters can send different frequencies into the ground. This allows locating cables at greater depths, or in a wider area closer to the surface. Lower frequencies, generally under 1KHz, are better at singling out targeted cables or circuits when multiple cables are present. They also penetrate deeper, but are affected by broken lines and complicated soils. Most locators operate at medium frequencies, between 8KHz and 33 kHz. To locate cables with broken lines and thick sheathing, transmitters are set to high frequencies, in the range of 40KHz to 300KHz.

cable locator Variable Frequencies
Source: lasersurveyingequipment.com.au

In-built GPS and Bluetooth

Underground cable locators with GPS allow for precision mapping of multiple sites. Cable locations can be overlayed on a Goggle Map and results are quickly and easily transferred to your phone using Bluetooth. Internal storage lets you store thousands of locates with the relevant data. Almost all underground cable locators have packaged software for downloading results on a PC and generating survey maps.

In-built GPS and Bluetooth Cable Locator
Source: constructionequipment.com


Several accessories provide detailed data about cable faults and damage and additional functionality. So-called A-frames are used to locate faults in cable sheathing and separate sondes for finding non-metallic pipes and conduits.

Using an Underground Cable Locator

To locate an operational power cable with a flowing current, a simple passive locator is more than up to the task. For searches that require more precision, like broken or damaged lines in areas with heavy cabling, an active underground cable locator can use multiple frequencies to pinpoint the cable at fault. Locators can be used with a direct connect line to the cable, a signal clamp or wirelessly. Search modes for detecting cables include Peak and Null modes. Peak modes use the highest available sensitivity levels in locating cables and are best at finding cables at greater depths. The Null mode alerts users when directly over a power cable or communications line. High-end locators can be switched between search modes to precisely detect the exact location, depth and direction of a cable. Readings in both modes, aided with left and right arrows, are presented during location on the display screen.

Underground cable locators are extensively used by utility companies and developers in surveying land primed for development. They’re also prized tools in renovations requiring excavation work and help avoid damage to existing power and telephony lines.

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