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|Can I put a cesium magnetometer on an Unmanned Aerial Vehicle?
26th of March, 2015
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Geometrics has many years of experience working with
autonomous vehicles (AUV, UAV, UUV, ROV, etc.) for magnetic surveying in the
search for minerals, geothermal resources, UXO and related fields of interest.
The main questions customers have are “What is the right magnetometer for my
application?” and “What platform should I use?” The answers vary case by case.
Geometrics offers several airborne magnetometer options for use
in an UAV (Unmanned Aerial Vehicle), including our models G-822, G-823, G-824
and G-862. The G-822 is not typically integrated with UAV’s primarily because
this magnetometer system requires an external counter, which in most cases is
not miniaturized sufficiently for use on small platforms. Geometrics has solved
this problem with the development of the internal Larmor Counter available as
the CM-201, CM-221 or CM-321 depending on magnetometer model.
The G-823 (a variant of the G-822) includes the CM-201
counter and is frequently used by UAV operators. The basic specifications for
this instrument are a user selectable sample rate (typically run at a 20 Hz
sample rate), 0.004 nT/√Hz RMS sensitivity and RS-232 data output. The G-823 is
supplied in two different versions (A and B). The G-823A system are selected on
the basis of their low heading error performance goes through rigorous sensor
heading error testing procedure (less than 0.15 nT Peak to Peak over 360
degrees spin), while the B sensor heading error is less than 1.0 nT Peak to
Peak but otherwise unspecified. The B version is intended for base station
operation, or on moving platform installations where active magnetic compensation
will be applied. We will expand on this in the following paragraphs. The B
sensor is also offered at a lower price than the A sensor. In most cases the
UAV will have magnetic influence on the magnetometer readings which will likely
be the dominant source of noise in the data, possibly many times greater than
the noise from the heading error of the sensor. In situations where the
platform’s contribution to the total heading error is high we suggest using the
economical B sensor because its influence on the compensated results will not
be distinguishable from the performance provided by the A system.
The G-823 (A or B) requires power from a 24 to 33 VDC source
and will draw 1 amp at 24 V on start. Then, after a few minutes (perhaps 3
minutes depending on outside temperature and guaranteed to be no more than 15
minutes at an ambient temperature of -30 C), the current draw will drop to
about 500 mA. The sensor and electronics bottle weight 2 kg in total. Data is
output via RS-232, typically at 20Hz. The G-823 does not store the data it
generates and so it must be connected to the system’s data logger. The G-823
also provides the ability to convert analog signals provided by other devices
and convert these to digital values at the same rate it measures the magnetic
field and report those values along with the magnetic field measurements. External
analog signals can be digitized using one of the 6 available 12 bit (4096 steps
over 5VDC) A/D channels provided.* See Attachment for complete Answer - more information on G-824, G-862, RBS Datalogger Box, MagComp and MFAM
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