16
signal strength drops abruptly, the conductor may have changed direction or stopped.
10 When you have pinpointed the conductor's location, mark it as required. See Section 4.5 for APWA
color markings.
11 When you have finished the locate, turn the Transmitter and Receiver off and disconnect the
accessories.
4.2 Inductive Coupling with the 4820 Metroclamp
Use this method if Direct Connection is not possible, but you can position a Metroclamp around the
conductor you want to trace. The Inductive Coupling method uses the 4820 Metroclamp to induce a signal
onto the conductor when direct metallic contact is not possible. The clamp is placed around the target
conductor. The Transmitter then induces a signal through the clamp.
When using the Metroclamp the conductor must be well grounded, i.e. with sheaths and neutrals. When
tracing lines that have insulators, the insulators should be bypassed, using the supplied jumper cable.
1 With the Transmitter OFF, plug the 4820 Metroclamp cable into the COND/AUX jack on the 480BB
Transmitter.
2 Place the Metroclamp around the conductor, below the electrical ground. See Figure 4-4. Make sure
that the clamp jaws are completely closed.
Figure 4-4: Inductive Coupling with the Metroclamp
3 Continue your locate by following steps 4 through 11, Section 4.1 Direct Connection.
4.3 Inductive (Indirect Method)
If you cannot make a direct connection onto the conductor, or use the Metroclamp, use the antenna that is
mounted on the Transmitter case to induce signal onto the conductor.
This is the least preferred method of inducing signal onto a conductor because the signal is broadcast
through the soil and air and can be picked up by other conductors in the area. In this mode the signal
radiates from the antenna mounted on the transmitter case and couples to the conductor by electromagnetic
induction.
