Wire Tracers

As the number of buried and hidden utility lines continues to increase, locating them becomes a greater challenge. Power, gas, sewer, and telecommunications lines clutter the ground beneath our feet and crisscross the walls of most structures. Finding and identifying these lines is a crucial step prior to construction or maintenance projects to ensure the safety for your crew while reducing the potential for costly mistakes. Wire tracers and cable locators are specifically designed to aid in locating energized and de-energized wires, cables and pipes whether underground or hidden in a wall.

Wire Tracer / Cable Locator Technology

Wire tracers / cable locators do not detect metal objects like a magnetic detector does. Rather, they rely on the target having a charge or signal placed on them which is detected by a receiver within the locator. Many utilities emit a charge or transmit a signal when lines are energized. In many cases each line has a different signal that easily distinguishes between different lines.

In cases where lines are not marked, many wire tracers are able to induce a signal onto the line using a transmitter in order to find it. Generally, the target must be metallic in order to conduct the signal, though a sonde or mini-transmitter can be used with plastic pipes. To induce a signal onto a pipe or cable, the transmitter is most commonly connected directly to the line or pipe to be located using signal clamps or clips. The signal will then travel down the pipe or cable. In areas where there is no access to the line, the transmitter can also induce a signal from above, through the ground to reach the utility.

Wire tracers / cable locators are generally available as single- or multiple-frequency units. Each unit has its advantages and limitations.

Single-frequency cable locators consist of a transmitter that induces a single high-frequency signal. The signal is picked up by the underground line and radiated back to the receiver. Single-frequency systems work well on lines and pipes in areas that are not congested since the high frequency has the tendency pick up everything underground, producing a distorted signal and making it difficult to distinguish between power, gas or communications lines. Another limitation is that single-frequency locators cannot determine the depth of the line.

Multi-frequency cable locators allow users to tune the transmitter frequency to the material used in the construction of the line or pipe they are trying to locate. Iron, copper, and aluminum each respond better to different frequencies making a multi-frequency locator better at distinguishing individual lines from one another. Multiple frequencies also make easier a wider range of tasks as higher frequencies are better for picking up more signals while lower frequencies make it easier to follow a particular line. Most multi-frequency locators can also estimate the depth of the line or pipe.

Some cable locators include a current measurement index that measures the current being put onto the line which helps distinguish the line from others and ensures users are staying on the original line… especially useful in congested areas where lines are crossing over one another.

Using a Wire Tracer / Cable Locator

Depending upon the application, there exists a range of cable locators from which to choose. Some are designed for use for underground lines and pipes while others better suited for the tight confines of a wall (wire tracers). As described above, cable locators usually include a transmitter (to induce a signal) and a receiver (to read the signal returning from the transmitter of the signal emitted by the line). Matching the locator to the specific application is the first step towards properly using it.

There are two primary methods of sweeping for lines and pipes with a wire tracer / cable locator.

Active locating involves searching for a specific line by using either a direct connection or by inducing a signal. The locator is either attached directly to the line or, if a direct connection is not possible, a frequency is selected and induced into the ground and reradiated by the utility. Active locating is for instances where a specific line or pipe must be located for maintenance or repair.

Passive locating involves sweeping an area looking for unknown lines. The users simply scans the area with the receiver looking for utilities that radiate or re-radiate frequencies. Passive locating does not allow the operator to distinguish between the types of lines but is very effective for making sure an area is clear of hazards prior to digging.

When using a cable locator to find underground lines and pipes, ground conditions have a significant impact on the signal. Clays and damp soils are very conductive and help provide a stronger signal with less interference. Dry soils, on the other hand, are poor conductors making it more difficult for the signal to travel down the line or pipe increasing the possibility of distortion or interference. Sometimes, simply adding water to the ground near the transmitter is enough to improve signal strength.

Things to Consider When Purchasing a Wire Tracer / Cable Locator

• Is it to be used primarily for finding lines and pipes underground or inside a wall?
• Is any special training needed to operate?
• Will the unit be used more for active or passive locating?
• Are any additional accessories, such as signal clamps or clips, needed?
• Is the frequency suited for the materials used in the pipes and lines to be located?
• Does the locator have filters to avoid cluttering signals?

If you have any questions regarding cable locators / wire tracers please don't hesitate to speak with one of our engineers by e-mailing us at sales@instrumart.com or calling 1-800-884-4967.