Locating cables and pipes: Part 1

Follow Avatar Anthony Caplin
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This section introduces the principals and techniques of locating buried cable and pipe utilities with the RD7000+ system. For more information on the theory of cable and pipe location, refer to The theory of buried cable and pipe location which is available to download from radiodetection.com



The RD7000+ locator supports a range of active and passive frequencies.

For a complete list of supported frequencies, refer to the RD7000+ Locator Specification datasheet.

Passive Frequencies

Passive frequency detection takes advantage of signals that may be present on buried metallic conductors. Dependent on the model, RD7000+ locators support up to three types of passive frequencies: Power, Radio and CPS (DLM model only).

You can detect these frequencies without the aid of a transmitter if they are present on the utility you are surveying.

Active Frequencies

Active frequencies are applied to a buried conductor using the transmitter. The transmitter can apply a signal using three methods:

Direct Connection

In Direct Connection, you connect the transmitter output directly to the utility. The transmitter will then apply a discrete signal which you can locate using the locator. This is the preferred method of applying a transmitter signal to a utility and in the majority of applications will apply a stronger signal to the utility, which may increase the locate distance.

To directly connect to a non-energized conductive utility:

  1. Switch the transmitter off.
  2. Connect the Direct Connection lead into the transmitter accessory socket.
  3. Clip the red connection lead to the utility ensuring that the area around the connection is clean and that a positive connection is achieved.
  4. Clip the black connection lead as far away as possible and at 90° to the ground stake or suitable ground point nearby ensuring that a positive connection is achieved.
  5. The display will show the Direct Connection lead connected icon.

Direct Connection Lead Icon

WARNING! Direct Connection to live conductors is POTENTIALLY LETHAL. Direct connections to live conductors should be attempted by fully qualified personnel only using the relevant products that allow connections to energized lines.

WARNING! The transmitter is capable of outputting potentially lethal voltages. Take care when handling the terminals, connection leads and ground stake, notify other technicians working on the line of the hazard and guard exposed conductors to prevent accidental contact.


In this mode of operation the transmitter is placed on the ground over or near the survey area. If a Direct Connection lead or signal clamp is not plugged into the transmitter, it will automatically go into induction mode. In this mode, only frequencies applicable for induction mode will be made available as the key is pressed.

Once activated the transmitter will induce the signal indiscriminately to any nearby buried conductors.

Please note that these signals will also be airborne and it is advisable to keep the distance between the transmitter and locator at least 10m / 30’ – this distance may need to be increased, particularly if depth measurements are taken.

Signal Clamp

An optional signal clamp can be connected to the transmitter and clamped around a cable or pipe to apply the transmitter signal. This method of applying the transmitter signal is particularly useful on insulated live wires and removes the need to disconnect the supply to the cable. Clamps are available up to 8.5” / 215mm in diameter.

WARNING! Do not clamp around uninsulated live conductors.

WARNING! Before applying or removing the clamp around a power cable, ensure that the clamp is connected to the transmitter at all times.


Selecting frequencies

It is important to select the correct or appropriate frequency for your particular application.

To select a frequency on the locator:

  1. Press the key to cycle through available frequencies.
  2. Alternatively, hold down the key and press the or keys to cycle up or down the range of frequencies.

If locating using an active frequency you must also set your transmitter to output the matching frequency.

To manually select a transmitter output frequency:

  1. Press the key to cycle through available frequencies.

NOTE: Some frequencies require that you connect an accessory, for example an A-Frame, before the frequency is available.