Our Irrigation & Locator Tools

501 Tracker II Kit

Trace wires and metallic pipes on active or dead systems without deactivating power.

551™ Advanced Underground Locator

Dual-frequency locator with IntelliTrack™ for tracing buried utilities up to 20 ft deep.

508S-G Wire Finder

Compact transmitter and receiver for locating wires in walls and shallow burial.

521E™ Wire & Valve Locator

Professional-grade tool for tracing buried wires, irrigation valves, and cable faults.

BLL-200 Buried Line Locator

Locate buried lines up to 20 ft and measure depth up to 15 ft with intuitive indicators.

What is a “Locator?”

“Locators,” which in this case is shorthand for Electromagnetic Line Locators, typically consist of a Transmitter which sends electrical signals into a conductor and a Receiver which detects the disturbances in the electromagnetic field above, even when the conductor is insulated and buried.

What is a Locator Used For?

Locators are used to reveal the placement of buried metallic assets. This is often either done with the purpose of damage prevention (knowing where is safe or unsafe to dig), damage repair (splicing, replacement, modification), removal of the asset, or access to controls (valves, vaults).

What Do Electromagnetic Locators Locate?

Buried lines/utilities that are commonly located include electrical cable, communications cable, tracer wire, irrigation control wires, and metallic pipes, but there are plenty of others; for instance, perimeter wires to trigger sensors for pet collars or robotic lawn mowers. Metallic snakes / fishing wire can also be inserted into non-metallic pipes to allow an electromagnetic locator to trace their paths.

How Does an Electromagnetic Locator Work?

The Transmitter sends a signal in the form of an electrical alternating current along lines or cables; the Receiver electromagnetically senses this signal above ground and provides audio/visual cues as you approach the line, letting you trace its path and detect its depth.

To learn more, please see our article Here

Basics of How to Use an Electromagnetic Locator

Where possible, directly connect the Transmitter to the conductor with one of the leads and to a ground stake in the earth with the other lead. The ground stake should be off to the side of the cable path at least a few feet. If you already have knowledge of the far end of the cable, then you have a great advantage if you can also ground that end too, using a spare cable and ground stake if necessary; the current in the cable will be maximized and you’ll be able to trace a strong signal all the way to the end.

When direct connection is not possible (no access to conductors, live voltage on the line, active service which can’t be disconnected, etc.), it is possible to inject signal into a metallic line by using an Inductive Coupler Clamp connected to the Transmitter. If there is no accessible portion of the line at all, an inductive antenna can broadcast signal to lines below.

With the receiver in hand, sweep in a 15–20-foot radius around the start of the cable for signal to determine the initial direction that the line runs.

When using a “peak” antenna receiver like the one included with the Tempo 501 (or 551 in peak mode), the receiver will give the strongest response over the line with the handle aligned parallel with the path. Follow this response to track the buried line.
If you are using a locator that operates in “null” mode, like the Tempo 521E (or 551 in null mode), the receiver will give a strong signal either side of the cable’s path but will have a distinct null directly over the cable. This mode is ideal for “pinpointing” the location of the cable and can also be used with a little understanding of geometry to determine the approximate depth of the cable.

What is an Irrigation Valve Locator?

An irrigation valve locator is designed with a low frequency transmitter signal and solenoid-sensitive “null” receiver antenna to find and isolate buried irrigation control wires and the solenoid valves they connect to, allowing you to quickly hunt down and uncover specific valves under turf or soil with ease.

Basics of How to Use a Solenoid Valve Locator

Disconnect the valve wiring from the controller and connect the transmitter to both a disconnected valve wire and a ground stake in the earth. With the receiver in hand, sweep in a 15–20-foot radius around the transmitter for signal to determine the direction that the wire runs from the controller. When using a “null” antenna receiver like the one included with the Tempo 521E (or 551 in null mode), follow a cancellation in tone between two peaks. When over a solenoid valve, the null in tone will give way to an extreme increase in signal (hot spot).

What is the difference between the 501 and the 521E?

The main differences between the 501 and the 521E involve the signal frequencies and orientation of the antennas in the receivers.

The 501 uses a very high-frequency signal at 447.5 kHz while the 521E uses a much lower 1.75 kHz.

The lower frequency of the 521E means there is less signal bleed so tracking a single wire in a bundle is easier (great for irrigation), but a lower frequency signal will struggle to travel to the end of a wire or cable if it is not buried (or grounded at the far end).

Meanwhile the higher frequency of the 501 is more susceptible to bleeding onto other nearby metal or wires, but it also allows for easier inductive transmission and puts out less current, therefore less risk of shock or damage as well as less power consumption by the transmitter.  The high frequency of the 501 will also work much better with fish tape / steel snake fed through a non-metallic pipe.

Furthermore, the 501 can also tend to track more deeply buried wires, cables and pipes when directly connected, but unlike the 521E, it does not require a direct connection; it can be used with the Inductive Clamp or Inductive Antenna.

What does the 551 add that the 501 does not offer?

The 501 is a very cost-effective and versatile locator which features a Peak antenna in the Receiver and transmits a single ultra-high frequency signal (447.5 kHz) via Direct Connection, Inductive Clamp Coupling or an Inductive Antenna.

Inductive Clamps allow signals to be applied to cables without disconnecting them — this is ideal for working with pipes and cables that are in use; just ensure that they are safely insulated. Inductive Antennas broadly emit signals which can be coupled to a cable or pipe below ground — great when you know there’s something down there but don’t have access to the ends of the line.

The 501 is an excellent “first-timer” locator which is intuitive and versatile, for most situations and applications.

The IP54-rated 551 offers a high-powered Dual Frequency Transmitter which uses one low frequency (1.75 kHz) and one mid-range frequency (33 kHz). Lower frequencies are helpful not only for tracking deeper depths and longer distances, but to limit the amount of “crosstalk” or “signal bleed” onto other nearby lines. Dual Simultaneous Frequencies are also excellent for pinpointing faults as you can instantly compare them along a line. One frequency may respond to damage differently than the other. Like the 501, the 551 also includes a coupling clamp and a built-in induction antenna, but while the 501 operates only at 447.5 kHz, the 551’s Inductive Clamp injects 33 kHz into a line and the 551’s induction antenna emits 133 kHz.

The 551 Receiver detects any of the three active frequencies (1.75 kHz, 33 kHz or 133 kHz) with both Peak and Null antennas—Peak to make tracing simple and intuitive and Null for pinpointing and triangulating depth. The 551 also Passively detects live lines carrying AC current. The IntelliTrack digital noise rejection feature ensures successful locating around electrical interference.

If more effectively isolating single lines, tracking deeper and further, detecting and pinpointing damage, intuitively triangulating line depth, and passively sweeping for live electrical current is desirable, then the 551 is the better choice, otherwise the 501 is simpler and more affordable.

What does the 551 add that the 521E does not offer?

The 521E is a capable irrigation and valve locator that transmits a single low frequency (1.75 kHz) and uses a Null antenna. It’s simple, entry-level, and excels at tracing single wires, finding solenoid valves, and detecting damage in most scenarios.

By contrast, the 551 Transmitter offers dual simultaneous frequencies and three application methods (Direct, Clamp, Antenna), and its Receiver sports both Peak & Null antennas, a Passive AC-detect mode, and IntelliTrack noise rejection.

These extras let the 551 handle challenging tasks such as:

• Rejecting interference from nearby power lines (IntelliTrack)
• Tracking short lines or fish tape inside non-metallic pipes using 33 kHz
• Pinpointing splices or faults by comparing frequencies
• Applying signal to 2-wire systems without disconnecting (Clamp)
• Sweeping for any buried utility before digging (Passive mode)

If you want simple valve locating on the job-site, the 521E is perfect and pocket-friendly—if you need more versatility and advanced features, the 551 is the clear winner.

Tempo Communications sets the standard for quality utility marking, underground locating, fault finding, and troubleshooting equipment at an easily accessible price point. Designed and assembled in the USA, Tempo’s buried markers, line locators, and irrigation testers combine capability and durability in simple, portable packages—delivering exceptional value for professionals.