Pipe location: 512 Hz sonde vs multi-frequency locator
Accurately finding the route of a buried pipe and marking the exact position of a fault are two different operations. Knowing which tool to use in each situation saves excavation time and reduces the margin for error.
The 512 Hz sonde integrated in the camera head
All Otter Store push camera heads include a built-in 512 Hz sonde transmitter. This sonde emits a low-frequency electromagnetic signal that can be picked up from the surface by a suitable receiver, even through pavement, soil or concrete slabs.
The process is very straightforward: while the operator advances the camera inside the pipe, a second operator walks the surface with the receiver and tracks the signal. When the point of maximum signal strength is detected, they mark the exact position of the camera on the ground — and therefore the fault location identified during the inspection.
When the 512 Hz sonde is sufficient
- ✓ Pipes at depths of up to 3–4 metres under normal pavement
- ✓ Marking individual faults during CCTV inspection
- ✓ Private installations, domestic drains and small diameter networks
- ✓ Environments with little electromagnetic interference (residential areas, parks)
The independent multi-frequency locator
A multi-frequency locator is a higher-specification instrument that operates on several frequencies simultaneously — both active (512 Hz, 1 kHz, 33 kHz, 83 kHz) and passive (50/60 Hz, radio). This enables it to detect and differentiate between various types of buried services: sewer pipes with a sonde, electrical cables, metallic pipes, fibre optic and gas networks.
The Otter Store Multi-frequency Locator features a backlit LCD screen, lithium-ion battery, working depth of up to 8 metres and advanced operating modes (peak, valley, arrow) for differentiating crossing routes.
When you need the multi-frequency locator
- ✓ Network mapping before construction work or excavation
- ✓ Pipes at more than 4 metres depth
- ✓ Urban environments with electrical interference or multiple overlapping services
- ✓ Detection of metallic pipes without camera access (using the active transmitter)
- ✓ Differentiating parallel routes less than 1 metre apart
Comparison table
| Criterion | 512 Hz sonde (integrated) | Multi-frequency locator |
|---|---|---|
| Max. depth | 3 – 4 m | Up to 8 m |
| Accuracy in clean environment | ± 10 – 20 cm | ± 5 – 10 cm |
| Electrical interference | High sensitivity | High resistance (multi-frequency) |
| Requires camera access | Yes | No (passive/active mode) |
| Differentiates different services | No | Yes |
| Cost / simplicity | No additional cost (integrated) | Additional equipment |
| Typical use | Marking faults during inspection | Mapping and civil works |
The most efficient combination
In practice, inspection and network maintenance teams working in both private installations and public networks use both systems in a complementary way:
During the CCTV inspection, the sonde integrated in the camera head locates the fault with sufficient accuracy to mark the intervention point on the pavement. For work prior to excavation, or when there is uncertainty about the depth and exact route of the network, the independent multi-frequency locator allows the full route to be traced with greater reliability.
Not sure which equipment you need?
Tell us the type of network you inspect and your usual working conditions. We will recommend the most suitable solution with no obligation.
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