Vivax Metrotech 4.04.000170, User Handbook Manual

Page: 65 / 76

™
Page 57 of 66
5 The Loc3 Series Transmitters
5.7.1 Direct Connection Mode
The Direct Connection mode is automatically selected by plugging a connection lead into the output socket. An icon confirming
the direct connection mode is shown on the display. The wave in the icon fluctuates when the transmitter is operating. The direct
connection lead consists of two colored cables with clips and covers. The red clip must be connected to the conductor being
located, the black clip to a suitable ground such as the ground stake provided with the transmitter.
A good connection is indicated by a change in the beep rate from the speaker and the current reading on the display.
FUSE
Wherever a direct connection can be safely made without the risk of injury, damage to the customer’s plant, or the transmitter, it
is the best way of applying the transmitter’s signal.
The positioning of the ground connection can also influence the degree of coupling experienced. Ground connections generally
should not be made to other pipes or cables or above-ground metallic structures such as wire fences. In general, the lower the
frequency is, the further the signal will travel, and the less signal-coupling will occur. The most common frequencies used for
direct connection are between 512Hz/640Hz and 8kHz.
Regulations in many countries require that power output is limited above specific frequencies. The Loc3 series 5-watt,10-
watt, and 25-watt transmitters enable frequencies below 45kHz to be transmitted using as much as 5-watts,10-watts or 25-
watt output, depending on your transmitter, but frequencies over 45kHz are restricted to 1-watt. Using direct connection and the
higher power at the low frequencies helps significantly in achieving greater location distances. Direct connections should not be
made to cables carrying greater than 25V (or as your safety practices allow). The transmitter is protected (250V fuse) from stray
currents that may exist on the target line.
5.7.2 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 for use at frequencies between 8kHz and 200kHz (between 8kHz
and 9.82kHz for the 25-watt transmitter). 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.
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.