EM38 DATA CONVERSION AND COMPUTER INTERFACE BOARD
EM38 DATA CONVERSION AND COMPUTER INTERFACE BOARD
DESCRIPTION
The optional data conversion and computer interface module converts
the analog output signal from EM38 receiver into digital data and
sends the data together with other information to a data logging
computer via the on-board RS-232 port. The conversion and sending
are automatic and continuous, no trigger is needed.
INTERFACE CABLE
The RS-232 port is provided via a 10-pin circular socket mounted on
the EM38 body. A 10-position circular connector to 9-position sub-D
female connector cable is supplied with each system for connection
between EM38 and the data logging computer.
Only two lines are used from the one-way RS-232 communication.
These two lines are:
10-pin circular
from EM31
9-pin sub-D
to computer
function
H
pin 5
GROUND
D (TXD)
pin 2 (RXD)
RS-232 DATA
RS-232 CONFIGURATION
The port is configured as a Data Communication
handshaking is used. It is initialized as follows:
Baud rate:
parity:
data bits:
stop bit:
9600
none
8
1
DATA RATE
10 records per second (approximate)
1
Equipment.
No
EM38 DATA RECORD FORMAT
Each data record consists of 8 bytes detailed below:
Byte 1 (ASCII)
" T "
-- start byte
Byte 2 (information byte. See next section for marker, mode,
phase and range interpretation.)
Byte 3 (ASCII)
+ or -, sign of data
Byte 4 (ASCII)
thousand's
Byte 5 (ASCII)
hundred's
Byte 6 (ASCII)
ten's
Byte 7 (ASCII)
one's
Byte 8 (ASCII)
carriage return
INFORMATION BYTE INTERPRETATION
The bit format of the information byte is:
BIT
VALUE OR MEANING
7
1
6
MARKER
= 1
= 0
when trigger/marker switch is pressed,
otherwise
5
MODE
= 1
= 0
for vertical operation
for horizontal operation
4
GAIN
= 1
= 0
Gain=8
Gain=1
3
0
2
Q/I
= 1 for Quad-phase (conductivity) measurement,
= 0 for Inphase measurement
1
RANGE 2
= 1 for 1000 mS/m scale
= 0 for 100 mS/m scale
0
1
2
MULTIPLICATION FACTORS
RANGE 2 represents sensitivity as follows:
SENSITIVITY
RANGE 2
MULTIPLICATION FACTORS
1000
1
Conductivity
Inphase
-1/Gain
-0.0288/Gain
100
0
Conductivity
Inphase
-0.1/Gain
-0.00288/Gain
Multiply reading by above factors to obtain result in mS/m or ppt.
3
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