Full scale deflection is from 0 to 2.56 volts, which equates to values between -275  and +275 nano teslas (nT) as set in the data logger preferences, and matching the scale used in the control unit. During quiet periods I can reduce the data scale to make activity clearer on the screen, or increase the scale for larger events. Each vertical division represents 60 minutes data, the most recent being at the position of the white vertical time line, upload time being displayed in the panel above. 

The data plots from left to right. Data in front of the time bar shows the position of the magnetometer output trace twenty four hours previously.

Please note the magnetometer output is not calibrated. The displayed value in nT  represents either a positive or negative deflection from the center point, i.e. 0nT, and is therefore not an absolute value.  

Data acquisition is provided via a DATAQ DI-148U A/D converter, and Windaq software.

An introduction to geomagnetism can be found here  

A full description of the project and installation can be found here.