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5 Loc3 25-Watt Transmitter Functions and Operation
5.8.2
Clamp Mode
The transmitter signal clamp is a precise way to apply the locate signal. Clamps are generally used when it is impossible to
access the conductor to make a direct connection, but there is access to place the clamp around the cable. Clamps are also
used when it is not safe to connect because the target cable is live carrying electricity.
The clamp is a specialized inductive device sometimes known as a toroid or coupler. All clamps are optimized to work at
specific frequencies. In most cases, clamps are designed to be used at frequencies generally between 8kHz and 9.82kHz. The
transmitter will only allow the selection of a suitable range of frequencies for your clamp.
Plugging a Vivax-Metrotech clamp into the output socket will place the transmitter into the “Clamp” mode. An icon confirming this
is shown on the display and will flash when the transmitter is transmitting.
When using the clamp no ground connection is needed.
FUSE
WARNING
When applying the clamp to cables that carry electricity – be sure to follow your company’s safety
instructions and procedures. Beware that if applied around a high voltage cable – that cable may
induce a current in the clamp, causing it to snap shut or jump quite dramatically. Always apply clamps
carefully.
5.8.3
Transmitter Frequencies
The Loc3-25Tx transmitters are supplied with a predefined set of transmitting frequencies. The factory will preset the most
commonly used frequencies. Additional frequencies are available to be selected in the frequencies list.
5.8.4
Frequencies and Maximum Power Output
Frequencies power outputs
Loc3-25Tx
Direct connection 25-watt
:
32Hz - 9.82kHz
Pushbutton
Pushbutton
4Hz/128Hz
3Hz/128Hz
4Hz/8Hz/128Hz
4Hz/8Hz/512Hz
4Hz/8Hz/128Hz
8.19kHz
512Hz
128Hz
As with most manufacturers, signal clamps are tuned to specific frequencies and
will not
work over the complete range of
frequencies.
Frequencies are selected by pressing the “f” pushbutton, which toggles through the frequencies available in the current mode's
available frequencies. The frequency is automatically selected if you don’t toggle past it within two seconds.
The output current is shown in large characters on the display. To increase or reduce the current
output, press “+” or “-.” The vertical bar graph at the bottom of the display indicates which of the
seven current output steps is being used. If the transmitter can supply the requested current, the
bar will turn black. If the bar does not turn black, improving the ground connections or wetting the
ground where the earth stake is positioned may help. However, it may not achieve the current setting
requested because the line's impedance is too high for this setting. If this happens, it is best to select
a lower setting with a black bar, ensuring a stable output.
The impedance of the target line will limit the current being transmitted; therefore, it is not unusual
to increase the output level but see no increase in the currently displayed. This is not a fault with the
transmitter.
