24 Oct How the hell does a cable locator work?

How the hell does a cable locator work?

An electro magnetic (EM) pipe and cable locator is a set of equipment with two main pieces. A Transmitter, and a Receiver.

Essentially it works like this:

1. The transmitter creates a signal at a specific radio frequency. For example, lets say 33kHz.
2. The signal is put into the pipe or cable. This can be done in a number of ways depending on the type of utility and the access available to it. A common way to put the signal into a cable is with an induction clamp around a cable.
3. The signal travels along the cable. For this to work, the cable or pipe must be made from conductive material. Cables have copper inside them to conduct the signal. Pipes are often made from copper, steel and cast iron which can all conduct a signal.
4. The signal creates an electro magnetic field around the cable.
5. The electro magnetic field produces radio waves.
6. The receiver detects those radio waves. You tune your receiver to ignore all other frequencies except for that one that your transmitter is creating, 33kHz in our example.

So you put a signal into the underground cable with the transmitter. Then you walk around with the receiver tuned into that signal. The receiver will let you know when you’re on top of your target cable, allowing you to map out the entire cable as if you had x-ray vision.

What are they called?

• Pipe locator
• Cable locator
• EM (electro-magnetic) locator
• Cable avoidance tool

What can they locate?

• Electricity / Power
• Water
• Gas
• Telstra / Communications

What if the pipe or cable isn’t conductive?

It’s common for environments to have non-conductive pipes and cables present. For some of these, such as optic fibre, sewer or storm water you are able to insert a conductive rod into the pipe or conduit and trace that, for more information see this article on locating underground sewer pipes. For poly or PVC water and gas pipes, you will need to turn away from the trusty EM locator and turn to the Ground Penetrating Radar (GPR), for more information see this article on how Ground Penetrating Radar works.