User Manual

Appendix B. SDI-12 Commands/Changing Settings
B.1 SDI-12 Command Descriptions
B.1.1 Start False Echo Learn
The Start False Echo Learn command is an essential function during the
startup of the sensor. It is also used during testing if a problem is encountered.
The command allows the unit to learn about false echoes (noise) in the area.
With the False Echo Learn command, you enter the actual distance to the
water surface, as measured in meters or feet, depending on the unit setting.
The radar sensor then emits the short microwave pulses. Any echo occurring
0.5 m (1.6 ft) short of the distance you entered will be considered noise.
To start False Echo Learn, do the aXSFEL+nnn.nnn! command (where
nnn.nnn = the actual distance to the water) followed by the aD0! (Send Data)
command. TABLE 4-5 in Section 4, Quickstart, shows an example of the
command and response.
B.1.2 Set Water Stage
With the Set Water Stage command, you enter the initial depth of the water,
and the sensor will automatically measure the distance between the sensor and
the water surface. The water stage setting and the initial distance measurement
are used to calculate subsequent water stage measurements. Correct stage
measurements require that the water stage setting be in the same units as the
Units of Measure setting. You can find out if the sensor is set to meters or feet
by using the aXGU! (Get Unit) command.
To set the water stage, do an aXSS+nnn.nnn! command (where nnn.nnn = the
initial water depth) followed by the aD0! (Send Data) command. TABLE 4-6
in Section 4, Quickstart, shows an example of the command and response for
entering this setting.
B.1.3 Query/Set the Address
Valid addresses are 0 to 9; A through Z; and a through z. The factory default
address is set to 0. The address can be verified by sending the sensor the
Address Query command (see TABLE B-2).
TABLE B-2. SDI-12 Command for Querying the Address
Initial Command Response
?!
a<cr><If>
Where a is the current address of the sensor.
Change the sensor’s address by sending the sensor the aAb! command, where
“a” is the original address and “b” is the new address. TABLE B-3 shows an
example of the command and response for setting the address.
B-3