The article explains the fundamentals of locating buried assets using Electro Magnetic Fields (EMF). It covers signal generation, current flow, and the impact of ground conditions, emphasising the importance of understanding these principles for accurate asset location.
By Steve Wood, Senior Trainer and Assessor, CERTLOC
Introduction to Locating Buried Assets
In the world of Certified Locators, the term “signal” is fundamental. But what exactly is this signal? How is it generated, and what factors influence its behaviour? Understanding these intricacies is crucial for reliable asset location, ensuring we create a reliable signal that we can trace, place our marks accurately and avoid misidentifications.
The Nature of the Signal
At its core, the signal we use to locate buried assets is an Electro Magnetic Field (EMF). You may have heard terms like EMF locator, EMF locating, or reliable EMF locate. Sometimes, it’s referred to as Electro Magnetic Induction (EMI). Although the concept dates back to the early 1900s, advancements in technology have enhanced our ability to apply, detect, and interpret these signals effectively.
Creating the Electro Magnetic Field
The EMF signal is generated by current, specifically Alternating Current (AC) for two reasons: inductance and capacitance. Any conductive object carrying current will have an EMF around it. However, for current to flow, we need two key components: voltage and a circuit.
Your EMF locator consists of a receiver and a transmitter, with the transmitter being responsible for generating the voltage. This voltage can be emitted at various frequencies, which we will discuss later. The goal is to create a current flow, where the voltage leaves the transmitter through direct connect, induction clamp, or spill induction—all of which operate differently and have unique challenges.
Establishing the Current Flow
The voltage applied to the target asset travels along the asset, into the ground, and back to the source, creating a current flow and consequently an EMF that we can detect. Unlike typical electrical circuits, where current travels through conductive material like copper wires, our current must traverse the ground. This introduces complexities like Far End Earthing and Capacitance, which we’ll explore further.
Challenges and Ground Conditions
Ground conditions significantly impact the amount of current and the resultant signal. No two locates will ever be identical due to these variables. Understanding these factors helps explain why signals might be weak, poor, or distorted—each presenting unique challenges. Additionally, an overly strong signal can create other issues that need addressing.
Becoming a Certified Locator
Becoming a Certified Locator requires a deep understanding of these principles. Over the coming weeks, I’ll delve into these topics in greater detail and invite your feedback, questions, and input.
Stay tuned for more technical tips and insights!