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EM61LX2 Data Logging System (DAS70-AR2)
1. Introduction
The Geonics EM61LX2 Data Logging System (DAS70-AR/LX2) consists of a field computer Ar-
cher2, data logging program EM61LX2wm (referred later as EM61LX2), and associated cable to
connect the Archer2 to the Geonics EM61-LX2 instrument. The program EM61LX2 is designed
for field computers Archer2 with the MS Windows Mobile V6.5 operating system.
The EM61LX2 program acquires and records survey data from the EM61-LX2 system, under the
control of the operator. It also records various field information such as survey line number (line
name), starting station, increment, comments, etc. Data is displayed in graphic and text mode.
Readings are displayed in real time in mV. In addition, the program allows you to monitor the in-
strument output while data is not recorded. Readings can be automatically recorded or displayed in
Monitoring mode at user specified time intervals. The EM61LX2 program continuously monitors
the condition of the instrument battery, without leaving the program. The EM61LX2 also provides
the possibility of automatic nulling of the instrument output at any time during the survey.
The program provides two types of graphic displays, modulated ribbon graphs or profiles. It can also
display measured channels Early (ChE) and Late (ChL), or Filtered (ChF) for each sensor. Type of
graphic display as well as set of channels (E and L, or F) can be toggled at any time during Monitor-
ing instrument data. Furthermore, for two sensors channels are named for the left sensor: ChLE
(Left-Early), ChLL (Left-Late), and similarly for the right sensor: ChRE (Right-Early) and ChRL
(Right-Late). It is always assumed that the left sensor is on the left (and the right one on right) of
center point while facing direction of a system movement. In case of GPS based positioning it is
the only method to determine proper location of each coil.
The EM61LX2 will accept NMEA-0183 compatible data from the Archer2 built in GPS receiver
or external GPS directly connected to an Archer2 field computer. GPS data which are embedded in
the EM61LX2 data file can be processed later in the Geonics DAT61LX2 program. The connected
GPS must be able to stream NMEA-0183 compatible messages. The EM61LX2 uses two NMEA
messages GGA and GSA. While message GGA is mandatory, the GSA string is used only to provide
information related to the GPS signal quality during data collection.
The EM61LX2 program records data together with a time stamp at each station. Data files created
with this program can be used to position a survey according to locations recorded separately by a
Global Positioning System (GPS). Survey setup parameters are saved in a configuration file, therefore
they can be automatically used during subsequent data collection sessions.
The program has an option that allows you to view data files. Data files are saved to the program's
data directory My Documents/DATA61LX2 by default. Data file names, which can be set by the
program based on the computer clock or user specified, have extension names L61. Files can be
transferred to a PC computer using a memory card, or by an USB port using the MS ActiveSync
or Central Point program.
The maximum speed of data collection is approximately 18 readings per second assuming 1 or 2
Hz GPS input.
