WHAT IS AN ELECTROMAGNETIC (EM) LINE LOCATOR?
Electromagnetic line locators operate by locating either a background signal or by locating a signal introduced into the utility line using a transmitter. There are three (3) sources of background signals which can be produced. A utility line acts like a radio antenna, producing electrons which can be picked up with a receiver (Radio frequency). Current carrying conductors have a 60HZ signal associated with them. This signal occurs in all active current power lines regardless of voltage. Utilities in close proximity to power lines or used as grounds may also have a 60HZ signal which can be picked up with a receiver (Electromagnetic).
Sondes are used to locate nonmetal sewer pipes, storm drains and conduits. Sondes also are used to locate cast iron drain pipe. A sonde is a small radio transmitter inserted into a pipe. Once inside, a conventional pipe locator is used to locate the sonde. The pipe’s position is then marked on the ground. The sonde is pushed further into the pipe, the receiver relocates the sonde and the pipe’s position is again marked. This process is repeated until the desired section of pipe is traced. Another option is to have a plumber snake the pipe. We can attach a transmitter to the snake and trace the line from the signal the snake emits.
EM UTILITY LOCATION METHOD
EM utility locators are used for tracing metallic pipes and utility cables and clearing drilling and excavation locations. These utility locators consist of a separate transmitter and receiver. The transmitter emits a radio frequency EM field that induces secondary fields in nearby metallic pipes and cables. The receiver detects these fields and accurately locates and traces the pipes, often to distances over 200 feet from the transmitter. Modern utility locators are also capable of providing approximate depth estimates of the pipes and sweeping areas for 60 Hz signal emanating from electrical lines.