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GSM19 Series Magnetometers - Version 7
GEM Systems, Inc. Advanced Magnetometers
For more technical information, visit www.gemsys.ca
12.
Press F-ok. The system returns you to the Survey menu.
1.1.3 Changing Time, Filename and Cycling
The time parameter controls the clock settings, and therefore, the time stamps that are placed in the
final output file. It is also required for performing base station corrections. Filename controls the
designated name of the file and is generally some specific value that is appropriate for the project at
hand (ex. 05survey.m or other value). The cycling controls the rate at which the magnetometer (or
gradiometer) samples.
13.
In the Survey menu, move the cursor to the time item and select it using C-change. Select C-
change and enter a new time in wyymmddhhmmss format. For a description of this format,
see the corresponding information in the User Guide.
14.
Move the cursor to the file item and select it using C-change. Type a new filename and use
the E-enter key to save the name. Note that the first two letters and the extension cannot be
altered; these are reserved for system defaults.
15.
Move the cursor to the cycling item and select it using C-change. The system toggles the
cycling settings as shown on the display. For walking mode, you should see settings such as,
“0.5 sec, 1.0 sec, 2.0 sec, etc.”
1.1.4 Setting the Tuning, AC Filter and Display Mode
With an advanced magnetometer, there will be some sort of “tune initialize” function that is
responsible for finding the precession signal (ex. similar to a radio station), and a second “auto-
tune” function that tracks the precession signal as it changes in amplitude.
With GEM, there are 4 possible states of the two controls, as follows:
Tune initialize
Autotune
Use When
Y
Y
Average magnetic field value at the survey location is
not known or alternately, as a default for maximizing
signal-to-noise ratios.
Y
N
Magnetometer is running automatically (ex. as a base
station) and there is some magnetic noise in the vicinity,
for example, from vehicles nearby. The magnetometer
may lose its signal when these extreme noise events
occur; however, it will recover gracefully as it will use
the “tune initialize” value for readings that follow.
N
Y
For fastest readings; reading time is minimized as the
system will not scan over the entire frequency range (i.e.
disabled). In addition, it is recommended for areas with
very high gradients; the magnetometer may saturate at
these points but will recover gracefully once the
magnetometer passes by anomalous zones. Another
possible use is with a base station where the unit is
stationary and the base unit does not have to handle large