Sutron Corporation 8310 & 7310 Users Manual 8800-1125Rev. 2.7 (BETA) 4/16/2014 pg. 217
SDI-12 Interface Standard
SDI 12 is a standard for interfacing to smart serial sensors. SDI-12 allows you to connect up to 10
sensors with as many as many as 9 parameters each. The interface is implemented using three
wires: Data, Ground, +12V.
Grounding
The ground conductor of the SDI-12 interface line should be large enough to keep the voltage
drop between the data recorder and the sensor to less than 0.5 volts during the maximum
sensor current drain. Failure to observe this specification will cause bad communications and/or
bad data.
Connector type
The connector type is not part of the SDI-12 specification. On the 8310, there are two
interconnected sets of SDI-12 connections. They are labeled SDI-12: GND, PWR, and DATA.
Communications
Communications rate is 1200 baud.
SETUP of SDI sensors
Each SDI-12 sensor has an address from 0 to 9. This address differentiates one sensor from
another. As they are shipped, they are almost always set to address zero (0). If/when you are
interfacing more than one sensor to the 8310, you must set each sensor to a unique address.
This is normally done by setting dip switches on the sensor, or by issuing SDI-12commands from
the front panel or terminal interface of the 8310. Failure to set unique addresses for each sensor
will result in failure of the communications interface, i.e. no data logged. Consult the sensor
manufacturer’s data sheet for information on your particular sensor(s).
SDI-12 commands to configure a sensor can be issued as follows: Navigate to the
Diagnostics/SDI Tools/Send SDI-12 command menu, and press SET/ENTER. Use the arrow keys
to set the characters of the command you want to send, and press SET/ENTER when done. The
reply from the sensor will be displayed.
Useful SDI commands
Resetting the address of sensors is normally done by sending the aAb! command, where a is the
current address of the sensor you want to change, and b is the address to which you want to
change. For example, 0A5! changes the address of sensor 0 to address 5.
Other initialization steps may be required for your sensor, prior to deployment. These may
include calibration, sample interval, etc. You may be required to use the sensor manufacturer's
test set for such operations.
The identification command can be used to help identify which SDI-12 sensors are connected.
The identification command has the form aI!, wher a is the address of the sensor. For example,
3I! commands the sensor at address 3 to return its identification string. Identification strings
typically include the SDI-12 version number supported., the manufacturer's name, the sensor
model number, the sensor’s firmware version number, and sensor’s serial number. This
command is ideal for determining whether the correct sensor is at a given address, and whether
that sensor is responding properly.
To Next Page
Loading...
