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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 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 512 Hz/640 Hz and
8 kHz.
Regulations in many countries require that power output is limited above certain frequencies. The Loc-5STx
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
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.
1.3.3
Clamp Mode
Plugging the signal clamp supplied by Vivax-Metrotech into the output socket will place the transmitter in
“Clamp” mode. An icon confirming this is displayed on the display. The icon flashes 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 sufficient 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 specific frequencies. In most cases clamps are designed to be used at frequencies generally between
8 kHz and 83 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.
1.4
Frequencies
1.4.1
Frequencies and Power Output
The Loc-5STx transmitter is supplied with a predefined set of transmit frequencies. The most commonly used
frequencies are preset by the factory. Additional frequencies can be added from the frequency select list. (See
section 1.4.2 for access to this menu)
Example of standard frequencies/preset at the factory are:
512Hz (where electrical systems are 60Hz) direct connection
– 5 watts.
640Hz (where electrical systems are 50Hz) direct connection
– 5 watts.
8 kHz direct connection
– 5 watt
33 kHz direct connection
– 5watt
65 kHz direct connection
– 1 watt.
83.1 kHz, 131 kHz direct connection
– 1 watt (depending on region).
200 kHz direct connection
– 1 watt (depending on region).
Some other frequencies with 5Watt output:
o
Direction connection: 256Hz, 491Hz, 982Hz, etc.
o
Direct and clamp connection : 8.19 kHz, 8.44 kHz, 9.5 kHz, 9.82 kHz, 32.8 kHz, 38 kHz
