™
Page 62 of 81
7 Loc3-5Tx Transmitter
FUSE
Wherever a direct connection can be safely made without the risk of injury, damage to customer’s plant, or the transmitter, it is
the best way of applying the transmitter’s signal.
The coupling of the transmitted signal to other pipes and cables in the area will be much less than with induction, although
where commonly bonded systems are encountered – coupling cannot be avoided.
The positioning of the ground connection can also inuence 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 512 Hz/640 Hz and 8 kHz.
Regulations in many countries require that power output is limited above certain frequencies. The Loc3-5Tx enables frequencies
below 45 kHz to be transmitted using as much as 5 watts output, but frequencies over 45 kHz are restricted to 1 watt. Using
direct connection and the higher power at the low frequencies helps signicantly 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.
7.3.3 Clamp Mode
Plugging the signal clamp supplied by Vivax-Metrotech into the output socket will place the transmitter in “Clamp” mode. An
icon conrming this is displayed on the display. The icon ashes when the transmitter is transmitting. When using the clamp no
ground connection is needed.
The clamp again is a precise way to apply the locating signal. It is generally used when access to the conductor cannot be
achieved to make a direct connection (but there is sucient access to place the clamp around the cable), or when it is not safe
to make a direct connection because the target cable is carrying electricity.
The clamp is a specialized inductive device (sometimes known as a toroid or coupler). All clamps are optimized to work at
specic frequencies. In most cases clamps are designed to be used at frequencies generally between 8 kHz and 200 kHz. The
transmitter will only allow the selection of a suitable range of frequencies for your clamp.
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.
To Next Page
Loading...
Need help?
General
