Active Frequencies
Active frequencies are applied to a buried conductor using the transmitter. The transmitter can apply a signal using these methods:
Induction Clamp
An optional signal clamp can be connected to the transmitter and clamped around a cable or pipe to apply the transmitter signal. This method of applying the transmitter signal is particularly useful on insulated live wires and removes the need to disconnect the supply to the cable. Clamps are available up to 8.5” / 215mm in diameter.
When to use Induction clamps:
- Clamps can be used where:
- Several cables or pipes run in close proximity to each other.
- A cable or pipe is accessible at an inspection hole or manhole.
Connecting an Induction clamp:
- Put the clamp connector into the accessory socket on the front of the RD7200 locator.
- Place the clamp around the pipe or cable and switch the locatoron.
- Set the frequency to the same as that on the transmitter.
- Put the clamp around each cable in turn and note the bar graph response. Compare the strength of response from each cable. The cable with a substantially stronger response than the others will be the cable to which the transmitter signal has been applied.
Direct Connection
In Direct Connection, you connect the transmitter output directly to the utility. The transmitter will then apply a discrete signal which you can locate using the locator. This is the preferred method of applying a transmitter signal to a utility and in the majority of applications will apply a stronger signal to the utility, which may increase the locate distance.
To directly connect to a non-energized conductive utility:
- Switch the transmitter off.
- Connect the Direct Connection lead into the transmitter accessory socket.
- Clip the red connection lead to the utility ensuring that the area around the connection is clean and that a positive connection is achieved.
- Clip the black connection lead as far away as possible and at 90° to the ground stake or suitable ground point nearby ensuring that a positive connection is achieved.
- Switch the transmitter On.
- The display will show the Direct Connection lead connected icon.
Choice of Frequency
- 512 kHz
- This low frequency is most useful for line tracing and identification over long distances. It does not couple easily to unwanted lines.
but - It is too low for induction, and it falls within the band of power frequency harmonic interference.
- This low frequency is most useful for line tracing and identification over long distances. It does not couple easily to unwanted lines.
- 8 kHz
- This medium frequency is the most useful general-purpose signal, high enough for induction, outside the power frequency interference band, and with limited coupling to wanted lines.
but - It may not be high enough to impose a strong signal on small diameter line like telecom cables.
- This medium frequency is the most useful general-purpose signal, high enough for induction, outside the power frequency interference band, and with limited coupling to wanted lines.
- 33 kHz
- This higher frequency is easily applied by induction to most lines, so is very useful for initial search. It travels on small diameter lines.
but
- This higher frequency is easily applied by induction to most lines, so is very useful for initial search. It travels on small diameter lines.
- It couples more easily to unwanted lines and loses its strength over shorter distances than lower frequencies.
- 100+ kHz
- This very high frequency range deals with the difficult cases – induction onto small diameter lines in dry sandy soil, and short lengths of cable. It is very easy to apply by induction
but
- This very high frequency range deals with the difficult cases – induction onto small diameter lines in dry sandy soil, and short lengths of cable. It is very easy to apply by induction
- It couples very easily to unwanted lines and does not travel far.
- It couples very easily to unwanted lines and does not travel far.