Using Accessories, Part 3: Stethoscopes & submersible antenna

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Large stethoscope High gain stethoscope Small stethoscope

When to use a stethoscope

At times, it may not be possible to put a clamp around a cable because of congestion or because of inaccessibility. A stethoscope antenna should be used in place of a clamp to identify the target cable(s).

How to use a stethoscope

Plug the stethoscope into the locator accessory socket. Press the concave head against each cable in turn to detect a maximum signal.

Stethoscope range

Large stethoscope antenna

The large stethoscope antenna, which plugs into the locator accessory socket, is used for cable identification in situations where the cable is exposed. It is particularly useful for identifying heavy cables lying in a tray where it is not possible to fit a clamp. The concave detector head on the end of the insulated, flexible gooseneck is placed firmly against the cable to be identified. If there are a number of cables, the stethoscope antenna will give the strongest response from the cable to which the transmitter signal has been applied.

Small stethoscope antenna

The small stethoscope antenna has a 25mm (2”) concave head at the end of a 2m (6½ ft) lead. The small stethoscope can be screwed into an extension rod or used at the end of several extension rods joined together for identifying inaccessible small cables.

Miniature hi-gain stethoscope

The miniature stethoscope is similar to the small stethoscope but has no handle or facility for extension rods.

The miniature stethoscope can also be used as a miniature antenna for locations where the bulk of the locator makes it inconvenient for use, such as locating pipes or cables in walls.

Submersible antenna

When to use a submersible antenna

Tracing buried pipes and cables across waterways and estuaries are frequent and critical locating applications. Less frequent but equally important is tracing and locating lines between the mainland and offshore islands. When locating pipes and cables the locator sensing antennas should be as close as possible to the target line so it is not practical to locate lines buried under a river or seabed from the surface. In most cases, it is necessary to measure the depth of cover to ensure the line is protected from dragging anchors or other underwater hazards.

The submersible, double depth antenna is suitable for use under water for tracing pipes or cables. There is a weight at the bottom of the antenna for stability and the unit has been pressure tested to IP68 to a depth of 100m (300ft).

The antenna is supplied with 10m of submersible marine umbilical cable as standard, but lengths of up to 100m can be supplied. The extra length enables the antenna to be carried by a diver on a riverbed or seabed while the locator is used in a surface vessel. It is crucial to have effective communication between the operator with the locator and the diver with the antenna.

Alternatively the antenna can be fastened to the end of a non-metallic boom from a barge and lowered to the riverbed or seabed.

How to use a submersible antenna

Apply the transmitter signal to the target line at an access point on the shore. The submersible antenna line for tracing the line underwater is plugged into the accessory socket of the locator. The locator is used onboard a boat, which should by positioned directly over the line. The transmitting signal should be applied by Direct Connection with the strongest possible signal and at the frequency that the submersible antenna is calibrated to. Make a ground connection about 50m (160ft) from the transmitter. Test the quality of signal on the line before locating on the water.

NOTE: The submersible antenna is calibrated to work at one frequency.

Tips for using a submersible antenna:

The user in the boat should be a specialist or have considerable experience using a locator so that they can give concise instructions to the diver.

It is prudent for the pair to practice working together on dry land before attempting to locate underwater. Using the antenna the diver should locate and trace a known line blindfolded receiving directions from the user with the locator out of sight of the line and the diver.

Because of rapid signal loss and a combination of large surface area and very conductive soil there may be problems applying a suitable signal for tracing a large diameter pipe. It may be necessary to use a high power, low frequency tracing signal.

It is necessary to define a method of recording target line position and depth before starting work in the boat or on the seabed.

Using a submersible antenna

WARNING: Only properly licensed and experienced divers should attempt to use the submersible antenna.


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