ES-2
7
COMMUNICATION
7
Communication
The ES-2 sensor can communicate using two different methods: 1)
Serial String or 2) SDI-12 communication protocol. This section dis-
cusses the specifics of each of these communication methods. Please
visit
www.metergroup.com
for the complete Integrator’s Guide, which
gives more detailed explanations and instructions.
7.1
Serial String
When you apply excitation voltage to the ES-2 sensor it makes a
measurement. Within about 140 ms of excitation, three measure-
ment values transmit to the data logger as a serial stream of ASCII
characters. The serial out is 1,200 baud asynchronous with 8 data
bits, no parity, and one stop bit. The voltage levels are 0 to 3.6 V and
the logic levels are TTL (active low). The power must be removed
and reapplied for a new set of clues to be transmitted.; The ASCII
stream contains two numbers separated by spaces. The first number
is EC in
µ
S/cm with a resolution of 1
µ
S/cm and the second num-
ber is temperature in Celsius with a resolution of 0.1
◦
C a carriage
return follows the three numbers, then the character “t,” indicating
that this is a ES-2 sensor, then a checksum character, and finally a
carriage return and line feed.
7.2
SDI-12 Communication
The ES-2 sensor also communicates using SDI-12 protocol, a three-
wire interface where all sensors are powered (brown wire), grounded
(bare wire and black wire), and communicate (orange wire) on shared
nodes ( for more information on the SDI-12 protocol, visit
www.sdi-
12.org
). Below is a brief description of SDI-12 for communication. If
you plan on using SDI-12 for communication with the ES-2 Sensor,
please see our integrator’s guide at
www.metergroup.com
for detailed
instruction.
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