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System Architectures

This page describes the main integration architectures for FG Sensors products. Each architecture is suited to a different use case — use the summaries and "when to use" notes to identify the right approach for your application.

Architecture 1 — FG-3+ / FG-4 to Microcontroller​

A single FG-3+ or FG-4 connects directly to a microcontroller with frequency/period counting capability. The MCU computes the field value and passes it to host software over USB serial.

flowchart LR
    A([FG-3+ / FG-4\nSensor]) -->|5V pulse\nfrequency output| B[MCU\nArduino / ESP32\nTimer input capture]
    B -->|USB Serial\nor UART| C[Host Software\nSerial terminal\nPython / MATLAB]
    C --> D[(Storage\nor Display)]

Signal chain: Sensor → frequency counting → field value in firmware → serial output → host software

When to use this architecture:

  • Custom embedded measurement systems
  • Low-cost single-axis or 3-axis data acquisition
  • Projects where you need direct control over sampling rate and processing
  • Integration with existing MCU-based platforms (drones, ROVs, robotics)
tip

For 3-axis measurements, use three FG-3+ sensors mounted orthogonally, or a single FG-4. Each axis requires one timer/counter channel on the MCU.

Architecture 2 — Sensor with Converter Circuit Board to ADC / DAQ​

The Converter Circuit Board converts the FG-3+ frequency output to an analog voltage, enabling direct connection to any analog data acquisition system.

flowchart LR
    A([FG-3+ Sensor]) -->|5V pulse\nfrequency output| B[Converter\nCircuit Board\nFrequency → Voltage]
    B -->|Analog voltage\nproportional to field| C[ADC / DAQ / PLC\nor Oscilloscope]
    C --> D[(Data Logger\nor Control System)]

Signal chain: Sensor → frequency-to-voltage conversion → analog input → ADC/DAQ → storage or control

When to use this architecture:

  • Connecting to existing analog DAQ hardware (NI, Measurement Computing, etc.)
  • Integration with PLCs that have analog input modules
  • Oscilloscope-based field monitoring
  • Systems where adding a microcontroller is not practical
  • Applications that already have analog signal chains in place
nota

The Converter Circuit Board eliminates the need for frequency counting in the downstream system. The tradeoff is an additional hardware stage and potential reduction in dynamic range versus direct digital measurement.

Architecture 3 — FG-3C Direct UART or Analog Integration​

The FG-3C provides a fully digital or analog-ready output, making it the simplest integration path for single-axis measurements.

flowchart LR
    A([FG-3C Sensor]) -->|UART 115200 baud\nASCII nT values| B[MCU RX pin\nor USB-UART bridge]
    A -->|Analog voltage\nor PWM| C[ADC input\nor DAQ channel]
    B --> D[Host Software\nor PC serial terminal]
    C --> D

Signal chain (UART): FG-3C Pin 4 TX → MCU RX → string parsing → field value in nT

Signal chain (analog): FG-3C analog output → ADC → field value via calibration

When to use this architecture:

  • Single-axis measurement with minimal hardware
  • Rapid prototyping — no frequency counting firmware required
  • Applications where an existing UART-capable MCU or PC is available
  • Low-component-count installations
nota

UART mode provides a calibrated digital output directly in nT, which is the simplest path to a calibrated measurement without writing signal-processing firmware.

Architecture 4 — Sensors to FGA Logger (Standalone Logging)​

The FGA Logger handles all sensor reading, GPS timestamping, and data logging internally. No external MCU or host computer is required during the survey.

flowchart LR
    A([Bartington Sensors\nB1 - 3 axes\nB2 - 3 axes]) -->|Frequency\npulse inputs| B[FGA Logger\nESP32 + GPS + SD]
    B -->|USB-C serial\nor DB9 UART| C[PC / Host System\nReal-time stream]
    B -->|FAT32 CSV\nmicroSD card| D[(SD Card\nCSV files)]
    D --> E[PolarWave DATA\nor QGIS\nor Python]
    C --> E

Signal chain: Sensors → FGA Logger → SD card CSV or USB serial → analysis software

When to use this architecture:

  • Field surveys requiring GPS-georeferenced magnetic data
  • Drone or vehicle-mounted gradiometer surveys
  • Autonomous logging without a connected PC
  • Applications requiring timestamped, multi-axis data with GPS coordinates
  • Integration with PolarWave DATA for anomaly mapping
tip

This is the recommended architecture for field survey applications. The FGA Logger handles all hardware complexity — you only need to process the resulting CSV files.

Architecture 5 — DIY Gradiometer with MAG-BOARD​

The MAG-BOARD handles two FG-3+ sensor assemblies and provides a real-time display and serial output, forming a self-contained hand-held gradiometer.

flowchart LR
    A([FG-3+ Sensor 1\nTop]) -->|Frequency| B[MAG-BOARD\nESP32 firmware]
    C([FG-3+ Sensor 2\nBottom]) -->|Frequency| B
    B --> D[LCD Display\nReal-time readout]
    B -->|USB Serial| E[PC / Data Logger]

Signal chain: Two FG-3+ assemblies → MAG-BOARD → LCD readout + USB serial output

When to use this architecture:

  • Hand-held or pole-mounted gradiometer surveys
  • DIY instrument builds using the Full Gradiometer Kit or Professional 3-Axis Magnetometer Kit
  • Applications requiring immediate visual feedback in the field
  • Educational and laboratory setups

Architecture Comparison​

ArchitectureAxesGPSStandaloneBest For
FG-3+/FG-4 → MCU1–3NoNoCustom embedded systems
Sensor → Converter → ADC1NoNoAnalog DAQ / PLC integration
FG-3C → UART/Analog1NoNoSimple single-axis digital output
FGA LoggerUp to 6 (2×3)YesYesField surveys, GPS logging
MAG-BOARD gradiometer2×3NoSemiDIY gradiometer, field use