G-856 Magnetometer — Common Procedures
 

This is a summary of some common procedures for the G-856 Magnetometers.  In general, these short-cuts refer to sections in the magnetometer manual (manuals are stored in the case of each magnetometer).

Notes about the organization of the magnetometer manual:  If anything the manual is overly verbose, use the table of contents to zero-in on what you want to do – otherwise the detail in the manual will drive you crazy.

Know which magnetometer you are using:  The department has three G-856 magnetometers, two are G-856XA’s, one is a G-856.  The older G-856 has less memory and lacks some options that the G-856XA’s have.  Appendix C in the manual describes the differences.  The G-856 also has been modified  to connect to an external battery source.

Magnetic units:  All UAF units read in nano-Teslas.  1 nano-Tesla = 1 gamma.
 

Quick Short Cuts:

A word in all caps indicates a button on the instrument, numbers are accessed by pressing the shift key.

Check Time:  Press TIME. The time HH:MM:SS will show for 5 seconds.

Change Time:  Press AUTO, TIME, SHIFT.
(Enter the Julian day using the numbers on the key pad.)
(Enter the hours and minutes)
Press ENTER.
Note that the G-856 is expecting 7 digits after the SHIFT key is pressed.

Erase All Data

Tune Magnetometer

Auto Tune Magnetometer
 

Operation Hints:

Predict the magnitude and “shape” of the anomaly which the target body will produce.  Estimate the size, shape, and magnetic  properties of the target.  This will indicate how to lay out your lines, what station spacing will work best and how careful you will need to be with your survey (will you need a base station?, how accurately should you record your data?, etc.).

If your survey will require highly accurate data (+/- 10 nT or less), then you should think about your field operations and how to minimize operator noise.  Some things to try:

Remove all magnetic material from the person holding the sensor.  If you have any doubts, test each item by:  Setting up the magnetometer in a magnetically-quiet environment with the sensor in a fixed position and moving suspect items up to the sensor while taking readings (try different orientations).

Always stand in the same orientation relative to the sensor (for example, always stand to the west of the sensor facing east) to minimize variation in spurious fields.
 

Revised January 2001