FGA Logger
The FGA Logger is a complete standalone data acquisition unit for 3-axis fluxgate magnetometer measurements. It accepts inputs from FG-3+ sensors, logs GPS-timestamped data to a microSD card, and streams data over USB and DB9 UART.
Hardware Overview
| Feature | Specification |
|---|---|
| Sensor inputs | 2 × 3-axis (B1 and B2 channels) |
| Sensor type | Bartington |
| GPS | Integrated GPS receiver |
| Storage | microSD card (FAT32) |
| USB | USB-C (power and serial data) |
| Serial | DB9 connector (UART) |
| Power | USB-C or external DC input |
Sensor Inputs
The FGA Logger accepts up to two 3-axis sensor assemblies (B1 and B2). Each sensor assembly consists of three Bartington sensors mounted orthogonally to measure the full 3-axis field vector.
- B1: First sensor input (X, Y, Z axes)
- B2: Second sensor input (X, Y, Z axes) — used in gradiometer configurations
In single-sensor configurations, only B1 is populated. B2 channels will output zero or null values in the CSV.
Signal Specifications
| Parameter | Value |
|---|---|
| Input type | Frequency pulse (FG-3+ compatible) |
| Input voltage | 5 V logic |
| Measurement axes | 3 per channel (X, Y, Z) |
| Output unit | nT (nanotesla) |
| Logging rate | Refer to firmware documentation for available rates |
| Resolution | Refer to FGA Logger datasheet |
Full logging rate and resolution specifications are available in the FGA Logger product documentation. Contact FG Sensors for detailed hardware specifications.
GPS
The FGA Logger has an integrated GPS receiver that provides:
- Latitude and longitude (decimal degrees)
- Altitude (meters)
- Satellites in view (SIV)
- Fix type
- HDOP (horizontal dilution of precision, in meters)
GPS data is logged alongside magnetic field data in every CSV row, allowing each measurement to be georeferenced.
Allow the logger to acquire a GPS fix before starting a survey. The LED indicator (see below) will indicate fix status. Logging without a GPS fix will record zeros or null values in the GPS fields.
SD Card
The FGA Logger logs data to a microSD card formatted as FAT32.
The FGA Logger only supports FAT32-formatted microSD cards. Cards formatted as exFAT or NTFS will not be recognized. Use a card capacity of 32 GB or less for reliable FAT32 compatibility, or format larger cards as FAT32 using a dedicated tool.
- Each logging session creates a new file on the SD card
- Files are written in CSV format — see Serial and CSV Formats for the full field description
- Remove the SD card only when the logger is powered off or logging has stopped
USB-C Interface
The USB-C port serves two functions:
- Power input — the logger can be powered from any USB-C power source (5 V)
- Serial data output — the logger streams CSV-format data over a virtual COM port when connected to a PC
Connect the FGA Logger to a PC with a USB-C cable and open the virtual COM port in any serial terminal or software (see Python Integration for an example).
DB9 UART Interface
The DB9 connector provides a hardware UART serial interface. This is intended for integration with external systems such as:
- Industrial computers
- Data acquisition chassis
- Custom embedded systems
| Parameter | Value |
|---|---|
| Connector | DB9 |
| Protocol | UART (RS-232 or TTL — verify voltage levels before connecting) |
| Baud rate | Configurable — refer to firmware documentation |
| Format | CSV text stream |
Verify whether the DB9 output is RS-232 level (±12 V) or TTL level (0/3.3 V or 0/5 V) before connecting to any external device. Connecting RS-232 directly to a TTL UART input will damage the receiving device.
LED Indicators
The FGA Logger uses onboard LEDs to indicate operating status:
| LED State | Meaning |
|---|---|
| Solid on | Power on, idle |
| Slow blink | GPS acquiring |
| Fast blink | Logging active |
| Off | Not powered or fault |
Exact LED behavior may vary with firmware version. Refer to the firmware changelog for updates.
Power Options
| Power Source | Connector | Notes |
|---|---|---|
| USB-C (5 V) | USB-C port | Standard USB power bank or wall adapter |
| External DC | Dedicated input | Refer to FGA Logger documentation for voltage range |
For field use, a USB power bank provides the most flexible and portable power source.