A Guide to Using Pipe and Cable Locators

A Guide to Using Pipe and Cable Locators

A Guide to Using Pipe and Cable Locators

Accurate detection and mapping of buried utilities are essential for preventing damage during excavation projects and ensuring the safety of construction workers. Electromagnetic pipe and cable locators are powerful tools that help professionals locate and identify these essential utilities. This guide aims to provide a comprehensive understanding of electromagnetic locators, their components, modes of operation, and best practices for using them effectively.

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What is an Electromagnetic Locator?

The most common type of Pipe and Cable Locator is the Electromagnetic Locator, they work on the principle of inducing an electrical current in the target utility, which then generates an electromagnetic field around it. The locator's receiver detects this field and helps pinpoint the utility's location. These locators are particularly effective for locating metallic utilities like pipes and cables.

Common use cases for electromagnetic locators include detecting water, gas, and power lines, as well as communication cables and fibre-optic lines.

Locator Components


The transmitter is responsible for generating the electrical signal used to locate utilities. The signal can be applied to the utility directly (direct connection) or induced using a transmitter coil (induction). Transmitters usually have adjustable power settings, allowing the user to control the strength of the signal based on the specific locating task.


The receiver is the device that detects the electromagnetic field generated by the utility. It processes these signals and displays the relevant information on its user interface, such as the signal strength, depth, and direction. The receiver is the primary tool for locating utilities and interpreting their position.

Locator Modes

Pipe and cable locators often have two primary modes: active and passive. Understanding when to use each mode is critical for effective utility locating.

Active mode:

In active mode, the locator's transmitter applies a signal directly to the utility or induces it via a coil. Active mode is generally more accurate and provides better control over the signal frequency and strength. However, it may require physical access to the utility or more setup time.

Passive mode:

In passive mode, the locator detects pre-existing electromagnetic fields generated by the utility, such as those produced by electric current flowing through power lines. Passive mode doesn't require a transmitter, making it quicker and easier to use in some cases. However, passive mode is generally less accurate and can be more susceptible to interference from nearby utilities or sources of electromagnetic noise. 

Choosing the appropriate mode for a project:

Selecting the right mode for a specific project depends on several factors, such as the type of utility being located, site conditions, and the level of accuracy required. Active mode is generally preferred when higher accuracy or more control over the signal is needed, while passive mode may be more suitable for quick, preliminary surveys or when access to the utility is limited.

Signal Frequencies

Selecting the appropriate signal frequency is essential for effectively locating pipes and cables. Different frequencies offer distinct advantages and limitations.

Low-frequency signals:

Low-frequency signals (typically below 10 kHz) can travel longer distances and are less susceptible to interference from nearby utilities or electromagnetic noise. They're ideal for locating larger, longer utilities or when working in areas with congested underground infrastructure. However, low-frequency signals may be less effective at detecting smaller, shallower utilities or distinguishing between closely spaced utilities.

High-frequency signals:

High-frequency signals (above 10 kHz) provide better resolution and accuracy for locating smaller or more closely spaced utilities. They're well-suited for detailed utility mapping or locating short sections of utilities. However, high-frequency signals may not penetrate as deeply into the ground, and they can be more susceptible to interference from other sources.

How to select the right frequency for a specific utility:

Choosing the appropriate frequency depends on factors such as the utility size, depth, soil conditions, and proximity to other utilities or sources of interference. In general, low-frequency signals are better for locating larger, deeper utilities or in congested areas, while high-frequency signals are more effective for locating smaller, shallower utilities or when greater accuracy is required.

Utility Depth Estimation

Accurate depth estimation is crucial for safe excavation and planning. Pipe and cable locators usually provide depth information based on the signal strength and angle of the detected electromagnetic field.

Factors affecting depth accuracy:

Depth accuracy can be influenced by factors such as the signal frequency, soil conditions, interference from nearby utilities or sources of electromagnetic noise, and the locator's calibration. Understanding these factors and accounting for them can help improve depth estimation accuracy.

Tips for improving depth estimation accuracy:

  • Select the appropriate signal frequency for the specific utility and site conditions.
  • Minimise interference by choosing the correct mode and adjusting the locator's settings as needed.
  • Regularly calibrate and maintain your locator to ensure optimal performance.

Pipe and Cable locator Accessories

Enhance the capabilities of your pipe and cable locator with various accessory options:

  • Signal clamps and couplers: These accessories help isolate the target utility and improve signal quality by reducing interference from nearby utilities or sources of electromagnetic noise.
  • Sonde transmitters: Sondes are small, self-contained transmitters that can be attached to a cable or inserted into a pipe to help locate non-conductive utilities or trace the path of a utility.
  • Trace Rods: A flexible rod which enables the detection of non-metallic drains, ducts or pipes when used in conjunction with a signal transmitter and cable locator. The Trace Rod is inserted and pushed along the utility under investigation. A Trace rod is ideal for tracing the path of small diameter pipes or drains, locating blockages or collapses in drains and locating or tracing non-metallic pipes that don’t produce a signal.
  • Property Connection Set: Used to apply a traceable signal to live electricity power cables when used in conjunction with a signal transmitter. This will enable you to trace the power cable around the outside of the property to the mains feed or outbuildings such as garages. The Property Connection Set is plugged in to a live power socket. A signal transmitter is used to apply a trace signal which is then detected by a Pipe and Cable Locator. This is ideal for quickly and easily identifying an electricity cable.

Soil Conditions and Interference

Soil types and conductivity can affect the performance of pipe and cable locators. Highly conductive soils, such as clay, can absorb and dissipate electromagnetic signals, making it harder to detect utilities. Conversely, sandy or rocky soils with low conductivity may allow signals to travel farther but can also result in false readings or ghost signals.

Electromagnetic interference sources:

Common sources of interference include power lines, radio signals, and metal structures. These sources can create electromagnetic noise, which may cause false readings or make it difficult to locate utilities accurately.

Strategies for minimising interference:

  • Choose the appropriate signal frequency and mode based on site conditions and the type of utility being located.
  • Adjust the locator's settings to filter out noise and improve signal clarity.
  • Use accessory tools, such as signal clamps and couplers, to help isolate the target utility and minimise interference.

Signal Interpretation

Understanding and interpreting the signals detected by your pipe and cable locator is crucial for accurate utility location.

Identifying false signals and ghost readings:

False signals and ghost readings can be caused by interference or reflections from nearby utilities or structures. Familiarise yourself with the typical signal patterns produced by the specific utilities you're locating and learn to recognise when a signal may be distorted or misleading.

Tips for accurate signal interpretation:

  • Use appropriate signal frequencies and modes based on the utility type and site conditions.
  • Adjust the locator's settings to filter out noise and improve signal clarity.
  • Employ systematic sweeping techniques to differentiate between true and false signals.

Pipe and Cable Locator Best Practices

Following best practices can help ensure accurate and efficient utility location:

Preparing the site: Clear the area of debris, vegetation, or other obstructions that may interfere with your locator's performance.

  • Optimal equipment setup: Choose the correct mode, signal frequency, and power settings based on the specific utility and site conditions.
  • Sweeping techniques: Employ systematic sweeping patterns, such as grid or serpentine patterns, to thoroughly cover the search area.
  • Marking located utilities: Clearly mark the location and depth of detected utilities using appropriate marking materials.
  • Proper documentation: Record the location, depth, and other relevant information about located utilities for future reference and to aid in project planning.

Locator Maintenance

Regular maintenance is essential for ensuring the reliability and accuracy of your pipe and cable locator:

  • Inspection and cleaning: Regularly inspect and clean the locator's components, including the transmitter, receiver, and accessories.
  • Battery care and replacement: Check and replace batteries as needed to ensure optimal performance. Follow the manufacturer's guidelines for proper battery care and disposal.
  • Calibration and performance testing: Periodically calibrate your locator and perform performance tests to ensure it meets accuracy standards.
  • Manufacturer recommendations: Follow the manufacturer's guidelines for maintenance, storage, and use to prolong the life of your equipment.

If you require any more information on understanding the principles, components, and best practices for using electromagnetic pipe and cable locators GlobalPos will be happy to help.

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