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6 Loc3-10Tx Transmitter
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 Loc3-10Tx enables
frequencies below 45 kHz to be transmitted using as much as 10 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.
6.3.3 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 also a precise way to apply the locating signal. It is generally used when it is not possible to access the
conductor 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.
6.4 Frequencies
6.4.1 Frequencies and Power Output
The Loc3-10Tx transmitter is supplied with a predefined set of transmit frequencies. The most commonly used frequencies will
be preset by the factory. Additional frequencies are available to be selected in the frequencies list see section 6.4.2.
Example of standard frequencies pre-set at the factory are:
● 512Hz (where electrical systems are 60Hz) direct connection – 10 watts.
● 640Hz (where electrical systems are 50Hz) direct connection – 10 watts.
● 8 kHz direct connection – 10 watt.
● 33 kHz direct connection – 10 watt.
● 65 kHz direct connection – 1 watt.
● 83.1 kHz, 131 kHz direct connection – 1 watt (depending on region).
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