Advanced Sonde Tracing: Plastic, Asbestos & 512Hz

A sonde provides a signal from a point inside a suitable pipe or duct, allowing a compatible receiver to locate the transmitter from the surface. Choose the sonde and receiver together: frequency, sonde mode, physical fit and the application all matter. There is no universal rule that 33 kHz reaches deepest or 512 Hz is only for shallow drains.

Match the exact frequency and receiving mode

A receiver must support the sonde's transmitted frequency and the appropriate sonde-locating mode. Do not assume that every CAT or precision locator receives every 512 Hz, 640 Hz, 8 kHz or 33 kHz sonde. The documented RD7200 and RD8200 specifications list supported sonde frequencies; use the specification for the exact receiver and revision.

Frequency is one selection factor. Sonde output, construction, receiving equipment, pipe material, ground and interference also affect performance. Published ranges belong to the particular sonde and test conditions; they are not a general depth guarantee for all products at the same frequency.

Check whether the sonde can do the physical job

• Confirm the sonde diameter, length and attachment method fit the access and intended carrier.
• Check the manufacturer's operating, pressure, temperature and environmental limits.
• Choose a battery or powered-sonde arrangement compatible with the actual equipment.
• Use an insertion and retrieval method suitable for the pipe and site.

A pipe being non-metallic does not make every sonde suitable. Access, obstruction, contamination and the surrounding environment remain relevant. Where asbestos-containing materials may be present, locating does not authorise disturbance: the site's asbestos assessment and controls govern that work.

Distinguish the main response from ghost signals

A sonde's signal pattern differs from that of a long energised conductor. The RD8200 manual describes a main response and ghost signals, with an orientation and verification procedure for identifying the sonde. Stopping at the first signal peak is not a reliable substitute for that procedure. Check the equipment and signal before insertion and follow the manual as the sonde is advanced.

A displayed depth is an estimate to the signal source under the specified conditions, not permission to excavate mechanically to that depth. Record and verify the result within the safe system of work.

Sonde, traceable rod or camera head?

A standalone sonde is a point source. A traceable rod system can support different route- or tip-tracing arrangements according to its connections and instructions. Some drain cameras contain a sonde, but the exact camera head and frequency determine compatibility; do not infer a transmitter from the camera's image resolution or cable length.

See how the information fits a survey in camera-sonde locating for drain repairs. Browse sondes and sonde locators alongside the precision locating range.

References

Radiodetection RD7200 technical specification V6, RD8200 technical specification V7 and RD8200 operation manual V7, sondes and depth; HSE HSG47; and HSE asbestos guidance.