1
EM61LX2 Data Logging System (DAS70-M2)
1. Introduction
e Geonics EM61LX2 Data Logging System (DAS70-M2) consists of a eld computer Mesa2 with
MS Windows 10 operating system, data logging program EM61LX2, and wireless Bluetooth con-
nection or associated cable to connect the Mesa2 computer to the Geonics EM61-LX2 instrument.
e program is prepared for the MS Windows 10 tablet Mesa2 (manufactured by Juniper Systems)
operated in the landscape as well as in portrait display mode (landscape mode is used in this manual
mainly). However the program can be used in other Windows 10( or 7) based eld computers with
vertical and horizontal oriented displays. e minimum supported display resolution is 800 x 600
pixels. In case high resolution display is employed, it is advised to set fonts to 125% or 150% to
increase legibility of the screen. e maximum size of program main windows is 1024 x 762 pixels.
e EM61LX2 program acquires and records survey data from the EM61-LX2 system, under the
control of the operator. It also records various eld 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 specied time intervals. e EM61LX2 program continuously monitors
the condition of the instrument battery, without leaving the program. e EM61LX2 also provides
the possibility of automatic nulling of the instrument output as well as calibrate Filter Channel
factors at any time during the survey.
e program provides dual graphic display - modulated colour ribbon graphs and proles. It can
also display measured channels Early (ChE) and Late (ChL), or Filtered (ChF) for each sensor.
Displayed set of channels (E and L, or F) can be toggled at any time during Monitoring 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. If one sensor is employed in the instrument then labeling
for Left sensor applies. In case of GPS based positioning it is the only method to determine proper
location of each coil.
e EM61LX2 will accept NMEA-0183 compatible data from the Mesa2 built in GPS receiver
or external GPS directly connected to the eld computer. GPS data which are embedded in the
EM61LX2 data le can be processed later in the Geonics DAT61LX2 program. e connected
GPS must be able to stream NMEA-0183 compatible messages. e 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.
e EM61LX2 program records data together with a time stamp at each station. Data les 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 conguration le, therefore
they can be automatically used during subsequent data collection sessions.
Data les are saved to the user selected data directory. Data le names, which can be set by the
program based on the computer clock or user specied, have extension names L61. Files can be
converted to LX2 format and viewed in DAT61LX2 program. Number of readings in a data le
is limited only by the hard drive capacity, however it is strongly recommended to avoid huge data
les (i..e one to two hours long data les are adequate). e maximum speed of data collection is
approximately 18 readings per second assuming 5 Hz (or less) GPS input.
