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GSM19 Series Magnetometers - Version 7
GEM Systems, Inc. Advanced Magnetometers
For more technical information, visit www.gemsys.ca
APPENDIX F: GSM-19T PROTON PRECESSION SYSTEM
The GSM-19T is a portable
standard
(without Overhauser enhancement) proton
magnetometer/gradiometer designed for hand-held or base station use for geophysical, geotechnical
or archaeological exploration, long term magnetic field monitoring at Magnetic Observatories,
volcanological and seismic research, etc. The GSM-19T is a secondary for measurement of the
Earth’s magnetic field, having 0.2nT resolution, and 1nT absolute accuracy over its full temperature
range.
The GSM-19T is a microprocessor based instruments with storing capabilities. Large memory
storage is available (up to 2Mbytes for version 5 and up to 32Mbytes for version 6 units).
Synchronized operation between hand held and base station units is possible, and the corrections for
diurnal variations of magnetic field are done automatically. The results of measurements are made
available in serial form (RS-232-C interface) for collection by data acquisition systems, terminals or
computers. Both on-line and post-operation transfer are possible.
The measurement of two magnetic fields for determination of gradient is done concurrently with
strict control of measuring intervals. The result is a high quality gradient reading, independent of
diurnal variations of magnetic field.
Optionally the addition of a VLF sensor for combined magnetometer/gradiometer-VLF
measurement is available.
F.1 MAGNETIC FIELD MEASUREMENT PROCESS
The magnetic field measuring process consist of the following steps:
•
Polarization: A strong DC (opposed to the RF polarization used on Overhauser enhanced units)
current is passed through the sensor creating polarization of a proton-rich fluid in the sensor
•
Pause: The pause allows the electrical transient to die off, leaving a slowly decaying proton
precession signal above the noise level.
•
Counting: The proton precession frequency is measured and converted into magnetic field units.
•
Storage: The result are stored in memory together with date, time and coordinates of
measurements. In base station mode, only the time and total field are stored.
Both series, GSM-19 and GSM-19T are used and operated in the same fashion. The main difference
between these models is the addition of an electron-rich fluid in the sensor and additional circuits to
achieve the Overhauser affect in the GSM-19 system.
* See Appendix A of this User's Manual for proton sensor orientation requirements.