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5 Operation
The NULL method is used for more accurate locating of the centerline of a conductor. You
would want to get an accurate locate of a conductor centerline before determining the depth of a
conductor.
PEAK and NULL procedures are described below.
5.2
Direct (Conductive) Connection
This is the preferred mode of operation because the transmitter is connected directly to a
metallic part of the conductor (hydrant, meter, riser, valves, sheath, tracer wire) allowing a strong
maximum signal to reach the conductor. In this operating mode the receiver can be closer to the
transmitter, and adjacent buried conductor interference is reduced.
5.2.1 Transmitter
1. With the transmitter OFF, plug the Direct Connect Cable into the jack labeled COND/AUX
OUTPUT on the VM-480B transmitter.
2. Attach the RED lead of the Direct Connect Cable to an electrically clean metallic part of the
targeted conductor.
3. Extend the BLACK lead of the Direct Connect Cable as far as possible from the conductor, at
a right angle. Look for a convenient existing ground, such as a metal street sign. Be careful
not to get close to or cross any adjacent buried conductors. If no existing ground is available,
use the ground spike as far into the Ground as possible, and attach the BLACK lead. If the
ground surface is too hard, place the ground plate on the ground and attach the BLACK lead.
To improve conductivity, put water and /or a weight on it.
Direct (Conductive) Connection
4. Pull the transmitter POWER Switch ON. Set the MODE switch to POWER TEST. The POWER
TEST LAMP should blink steadily, indicating a charged battery.
5. Set the receiver MODE switch to “Active”.
6. Set the receiver SENSITIVITY KNOB to a low setting on the left of the dial, adjusting as
needed for good signal reception. As you move farther away from the transmitter, you will
need to increase the sensitivity. It is important to tune the sensitivity as low as possible in
order to sharpen the reception and reduce signal bleed-off onto adjacent conductors.
7. Set the receiver RANGE knob to “NORM”, adjusting to “HIGH” when necessary.
Tx
1 Target Conductor
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