After exploring the top circuit breaker finders and trackers, it’s important to understand how these devices actually work. Many people, including electricians, may not be aware of the inner workings of these tools. To most of us, these little plastic boxes seem like magic. They have the ability to peer into walls and trace hot and open circuits. But what sets a circuit tracer apart from a circuit breaker finder? And why do some tools come with a higher price tag and more features? In this article, we aim to answer some of these questions and provide you with a deeper understanding of these tools.
Circuit Tracer vs. Circuit Finder
The term “tracer” doesn’t accurately describe a simpler circuit breaker-finding device. Tracers are typically used to trace the path of a circuit, allowing professionals to work on home remodeling projects without losing track of what’s happening behind the walls. These sophisticated devices are also used to find short circuits or trace wires inside conduit, both on energized (live) and de-energized (open circuit) circuits.
On the other hand, circuit breaker finders are generally designed for energized circuits. The transmitter is plugged into an outlet and draws a spike of current from the line, usually around 6-10 amps, for a very short period of time. This generates a strong signal. Consequently, the transmitter doesn’t require much complexity. Its primary function is to extract the current pulses that the receiver is designed to detect.
In terms of receiver sensitivity, it doesn’t need to be very high to identify a suitable circuit breaker. It doesn’t require much gain either, as it only needs to detect the current-carrying parts in the breaker and the tool, which are usually just an inch or two apart.
How Circuit Breaker Finder & Tester Works
Advanced tools like the Greenlee CS-8000 can trace live circuits up to 3-5 feet overhead. This is made possible by the circuit tracer’s high sensitivity, allowing it to adapt to both weak and strong signals. Different circuit breaker finders achieve their goals through various techniques. One approach involves injecting a signal burst at the transmit frequency and controlling the width of that frequency on the AC waveform. This is for live circuits. In the case of dead circuits, a burst of pulses at regular intervals is sent, alternating between a pulse and some quiet time. The receiver then looks for these distinct signatures.
Choosing the right frequency and modulation technique can be challenging, as you want to define something without too much interference. Nowadays, there are more potential sources of noise than ever before, such as computer UPS systems, fluorescent lights, and switching power supplies. The goal is to target something that doesn’t occur naturally.
Another technique involves applying the signal to the wire for a few full cycles and then removing it for a few cycles, repeating this process. This creates a distinct “label space” that the receiver can differentiate from any interference in the real world. Different tools may use different techniques or frequencies, but the underlying principles remain quite similar.
Why so sensitive?
Battery-powered circuit tracers don’t draw much current, so the receiver needs to be capable of amplifying and distinguishing the desired frequency. In contrast, circuit breakers produce a very strong signal, allowing for more leniency in terms of receiver sensitivity. A circuit tracer can detect both open and powered circuits simultaneously, requiring it to be able to differentiate between two different signals.
A complete circuit generates a magnetic field around the wire, which is tangible. Detecting an open circuit requires searching for the static field. Consequently, circuit tracers need two types of pickups. An inductor, such as a 100mH inductor, is used for the magnetic field, while a copper plate or an area on the circuit board is employed for static field detection.
At the Core
Both the transmitter and receiver contain microprocessors. The transmitters usually have simpler microprocessors, responsible for determining whether the line is energized or not. They also need to detect the AC waveform so that they know when and where to insert the burst. On the receiver side, the microprocessor has more tasks. It runs a digital filtering algorithm and controls the programmable gain amplifier to accurately capture the desired signal.
When a circuit tracer traces an overhead live circuit, the range of signals it encounters needs to be significantly more sensitive than when it’s at a circuit breaker. However, the tool should be capable of performing both functions. Therefore, the microprocessor needs to adjust the gain accordingly and do so quickly. In tools like the Greenlee CS-8000, the LCD screen’s “waterfall bars” are also controlled by the microprocessor. Regardless of the reading method, the microprocessor handles it.
Who Uses These Tools?
Anyone who has tackled renovations knows that residential and commercial buildings often lack proper circuit identification. While new buildings may have well-marked circuits, older buildings tend to be less accurate and detailed. If you need to trace a short to ground or find an overhead circuit, understanding how a circuit breaker finder works is crucial. These tools are invaluable for tracing wires, saving both time and effort when opening up spaces between rooms.
These tools also find utility in more sensitive areas such as hospitals, where interference is a significant concern. In such cases, using a high-quality circuit tracer becomes essential. Additionally, identifying the correct circuit breaker is even more critical, as it can prevent accidentally shutting off essential equipment like respiratory devices.
Pro Tool Reviews would like to express gratitude to Richard Duke, Greenlee’s Electrical Test and Measurement Product Manager, for taking the time to answer our questions about circuit breaker finders and tracers, as well as the technology behind these tools. If you’re a product manager with an interesting story to share about how a particular tool or technique works, feel free to reach out to us at editor-AT-protoolreviews.com. We’re always open to considering new articles or getting in touch with you for more information.