Geometrics Memory-Mag G-856AX, Operation Manual

Page: 8 / 60

Geometrics, Inc
.
G-856AX Operation Manual
2
our website includes general information on the use of magnetometers. It should be
studied as a companion to this manual which deals specifically with the G-856AX
Memory Mag
™ .
Terms used in this manual
The magnetic field intensity at the surface of the Earth has an average value of about
50,000 nano-Tesla (nT). Historically, one nT is sometimes referred to as a gamma or “

”.
Throughout this manual we will always express field intensity in nT.
The terms “sampling”, “cycling”, and “reading” all refer to the magnetometer’s
measurement of the field intensity. Note that these terms do not necessarily refer to both
measurement and internal storage of the measurement value.
The G-856AX
Depending on its particular configuration, the G-856AX can be a portable, man-carried
magnetometer, a gradiometer measuring the field with two sensors, or a "base station"
magnetometer. As a hand-carried instrument, it features simple, push button operation
and a built-in digital memory that stores over 5000 single sensor measurements or 2500
gradiometer readings. This relieves the user of the need to physically write down the data
in the field, eliminates transcription errors and most importantly, allows the use of
computers to automatically record and process the data from the magnetic survey.
Software Programs are available from Geometrics to help the user process and interpret
survey data. These programs include MagMap2000 and MagPick and are available for
download from our website:
www.geometrics.com .
The G-856AX can also record data automatically at regular intervals, so it can be left
unattended to monitor diurnal changes in the earth's magnetic field. These readings (up to
12,500) are collected at a base station and used to correct simultaneous field
measurements for high accuracy surveys. Measurement data from the G-856AX may also
be fed directly into an external computer. The time-of-day generated by the
magnetometer’s internal clock is recorded with each reading taken in either mode.
All operations are controlled from keys imbedded in a weatherproof membrane that
comprises the magnetometer console’s front panel. The key sequences for the various
magnetometer operations have been carefully designed to provide simple yet flexible
operation.
A single connector is used for the sensor signal input and data output. The output format
is in the universal RS-232 protocol that is accepted by most modern computers. Interface
software for downloading, profiling and gridding/contouring of data is provided by
Geometrics MagMap2000 software. A serial to USB converter is available for use with
computers that are not equipped with a serial port.
Physically, the G-856AX is compact and lightweight. It is weather proof and operates