Electromagnetic Locatinguses a transponder that transmits an extremely low voltage AC current onto a conductive material (ie. a pipe that is steel or polyethylene with tracing wire attached to it). The underground utility line can then be accurately located and traced with a wand-like receiver that detects the EM fields that have been created around the utility line. The receiver may also be used by itself to detect any current carrying conductors that have a 60 Hz signal associated with them, such as power and communication lines.
Principals of a electromagnetic locating system
Pros and Cons of Electromagnetic Locating Equipment: Pros: •Reliable when locating metallic utilities and electrically induced lines •Efficient and fast Cons: •Electromagnetic field created can “bleed” onto other utilities in busy areas, causing a difficult locate •EM needs an access point to “clip on” to the utility •Cannot locate plastic lines unless a tracer wire has been installed
An EM survey in process...
An EM locating system consisting of a transmitter and a reciever