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DIY Gradiometer Kit

FG Sensors DIY Gradiometer Kit

The FG Sensors DIY Gradiometer Kit is a complete system designed for building a fluxgate magnetometer gradiometer using FG-3+ sensors and the MAG-BOARD electronics platform.

The kit allows users to construct a portable instrument capable of detecting magnetic anomalies and buried ferromagnetic objects several meters underground. It is widely used in applications such as metal detection, archaeology, geophysical surveys, and experimental magnetic field measurements.

The system measures the difference between two magnetic sensors positioned along a tube. This configuration suppresses background geomagnetic variations and enhances the detection of nearby magnetic disturbances.

How the Gradiometer Works​

A gradiometer uses two sensors placed at a fixed distance from each other:

Upper Sensor
│
│
│ (sensor separation)
│
Lower Sensor

Instead of measuring the absolute magnetic field, the device calculates the difference between the two measurements:

Gradient = B_upper − B_lower

This approach allows the instrument to highlight local magnetic anomalies while rejecting uniform background fields such as the Earth's magnetic field.

Main Components​

The DIY Gradiometer Kit includes several key elements required to build the system.

FG-3+ Fluxgate Sensors​

Two FG-3+ fluxgate magnetometers measure the magnetic field along the sensor axis.

These sensors provide a frequency output proportional to magnetic field strength, enabling highly sensitive measurements of weak magnetic variations.

MAG-BOARD Electronics​

The MAG-BOARD is the central electronics module that:

  • reads the sensor signals
  • processes magnetic field data
  • drives the display and user interface
  • communicates with external software

The board comes with a preloaded firmware for gradiometer operation.

Mechanical Structure​

The gradiometer is mounted inside a tube that holds the sensors at a fixed distance.

Typical mechanical components include:

  • sensor holders
  • tube structure
  • electronics housing
  • mounting brackets
  • optional 3D-printed parts

The spacing between sensors allows the system to measure magnetic field gradients along the tube axis.

User Interface​

The system can include several interface elements:

  • LCD display for real-time readings
  • NULL button for calibration
  • sensitivity adjustment buttons
  • buzzer for feedback signals

These controls allow the user to adjust the sensitivity and calibrate the instrument during operation.

Smartphone Connectivity​

The DIY gradiometer system supports smartphone connectivity through the FG Sensors Android application, allowing users to visualize and analyze magnetic signals in real time.

The mobile app provides an easy way to monitor measurements and perform field analysis during surveys.

Typical Applications​

Metal Detection​

  • detecting buried ferromagnetic objects
  • locating underground structures
  • treasure hunting

Archaeological Surveys​

  • locating buried artifacts
  • mapping archaeological sites
  • detecting ancient structures

Geophysical Surveys​

  • magnetic anomaly detection
  • geological exploration
  • subsurface mapping

Educational and Research Projects​

  • magnetometer experiments
  • geomagnetic field measurements
  • sensor system development

Documentation Structure​

The DIY Gradiometer Kit documentation covers the full assembly and operation process:

  • assembling the MAG-BOARD electronics
  • configuring the firmware
  • mechanical assembly of the sensor tube
  • installing sensors and wiring
  • calibration and tuning procedures
  • final system assembly

Follow the next sections to build, configure, and calibrate the gradiometer system.