The fluxgate magnetometer has 0.01nT resolution each components. A different value between a calculated total field value by the fluxgate magnetometer and absolute total field is less than ±50nT accuracy. The analog/digital (A/D) converter has 32 bits resolution at a sampling rate of 250 Hz. Frequency of data acquisition is 10 Hz (average of 25 samples) or 1 Hz (average of 250 samples).

The fluxgate magnetometer finds the compensation field automatically on "POWER ON". When a large magnetic field variation exceeds 300nT, it adjusts the compensation field to fit the variation measuring range of ±300nT automatically.

In order to achieve long-term stability of measurement, the magnetic sensor unit is suspended by a gymbal and thermometers (0.01deg. resolution) are installed in the sensor and the circuit board. These data are recorded with the magnetic data.

The fluxgate sensor has a waterproof structure and it is possible to set it in the ground. Installing the sensor underground minimizes temperature change and ensures long-term stability.

The data logger has a network function (TCP/IP) and supports protocols of FTP, TELNET, PPP, and etc. The saved data in the data logger are transmitted by LAN network and remote controls for the system are possible. The data are saved in an SD memory card in the data logger as well.

Time control for the system is performed by GPS. The total accuracy against an accurate time is less than 1 msec.

The power supply has a floating charger. When a battery is connected, the measurement continues in a power failure.