sensors

Magnetic Collar (Contact)

Rugged contact-based sensor for monitoring maximum scour depth around bridge piers and abutments.

Model No
G93-800C
Sensing Length
Standard 2m to 5m (Customizable)
Resolution
100mm or 150mm (Sensor spacing)

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Overview

Rugged contact-based sensor for monitoring maximum scour depth around bridge piers and abutments.

The Geolook G93-800C Magnetic Collar is a reliable, mechanical-electronic hybrid sensor designed to measure the depth of scour (sediment erosion) around underwater structures. It is specifically engineered to track the 'maximum scour depth' reached during high-flow events or floods. The system consists of a stainless steel pipe installed vertically into the riverbed, equipped with internal magnetic reed switches. A weighted magnetic collar sits around the pipe at the initial bed level. As the riverbed erodes (scours), the collar slides down the pipe by gravity. The internal sensors track the collar’s lowest position, providing a definitive record of the erosion depth even after the scour hole has been partially refilled by sediment during lower flows.

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Benefits & Features

  • Passive operation—the collar moves naturally with the receding bed
  • Stainless steel 316L construction for extreme underwater durability
  • Magnetic reed switch array provides discrete depth increments
  • Records maximum scour depth even if the hole later refills with silt
  • No moving electronic parts; immune to turbidity and water clarity issues
  • Low maintenance; once installed, it requires no calibration
  • Vibration and impact resistant for high-flow environments

Detailed Description

The Challenge of Refilling Scour Holes

One of the greatest dangers in bridge engineering is 'refilled' scour. During a flood, the fast-moving water digs a deep hole around a pier. As the flood recedes, the water slows down and drops new sediment into that hole.

A post-flood inspection might show the riverbed is back to its original level, hiding the fact that the pier's foundation was recently compromised. The G93-800C solves this because the magnetic collar stays at the *lowest* point it reached, revealing the true maximum scour depth to the engineers.

Gravity-Driven Reliability

Unlike ultrasonic sensors that can be confused by debris or 'cloudy' water (high turbidity), the Magnetic Collar is a contact-based system. It does not rely on sound waves. It relies on gravity.

As the sediment supporting the collar is washed away, the collar simply falls. It is a foolproof method that works in the muddiest, most violent flood conditions where electronic 'non-contact' sensors often fail.

Installation & Integration

The sensor pipe is typically attached to the upstream face of a bridge pier using heavy-duty brackets or driven into the riverbed using a specialized mandrel. The internal wiring is hermetically sealed, allowing the signal to be sent to a Geolook GL-DL series data logger mounted safely on the bridge deck.

Early Warning for Bridge Safety

Scour is the leading cause of bridge failure worldwide. By integrating the G93-800C into a real-time monitoring network, bridge authorities can set 'Critical Depth' alarms. If the collar drops to a depth that threatens the foundation, the system can automatically trigger lane closures or speed restrictions, potentially saving lives.

Available Models

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Specifications

Model No
G93-800C
Sensing Length
Standard 2m to 5m (Customizable)
Resolution
100mm or 150mm (Sensor spacing)
Material
Stainless Steel 316L
Collar Weight
High-density weighted magnetic ring
Operating Temp
-5°C to +60°C
Signal Output
Digital Pulse / Resistance Chain