Vivax Metrotech FLS-2, Руководство пользователя

Страница: 54 / 58

™
Page 48 of 49
16 Glossary
16. Glossary
This chapter defines practical terms.
Active locating Locating an underground line through signals generated by the
transmitter.
Centerline
The imaginary line extends along the ground directly over the line to
be traced. Also, the center of the display indicates the locator is to
the left or right of the line.
Line direction East, West, or Line 1…16
Common-
bonded
conductors
Lines or ground conductors, such as telephone lines, power cables,
or pipes, are electrically connected. Conductors common-bonded to
the target conductor carry the signal, making it difficult to locate the
target beyond the common bond.
Current
measurement
A feature on the receiver, whereby an indication is given of the
current in the target line. The indication of the current does not
change as the depth of the line changes. Although the indicated
current decreases slowly as the distance of the receiver from the
transmitter increase, an abrupt change in the indicated current
may be caused by a lateral “T” or damage to the line. A current
measurement may also be used in a crowded environment to confirm
the signal is on the target line rather than coupled to an adjacent
utility.
Frequency The transmitter's electromagnetic field reverses its direction many
times each second. The signal's frequency is the number of these
cycles completed in one second. Proper frequency selection is
important for successful locating.
Frequency
allocation and
maximum
power
The permissible use of the electromagnetic frequency spectrum is
mandated by the Federal Communications Commission (FCC). The
Code of Federal Regulations, 47 (Telecommunications), Part 15,
section 15.213. The FCC regulates the frequencies and power levels
used to locate underground lines. Below 9 kHz, any power level may
be used. For 9-45 kHz, a maximum of 10 watts of power may be
generated by the transmitter. For 45-490 kHz, the transmitter may
generate a maximum of 1 watt of power.
Gain The amount of the signal at the receiver's antenna increases before
it is processed and displayed. The signal generated by the current
in the target line is very small. It must be increased in size before
generating a perceptible indication on the display or sound in the
receiver.