ADS-270 User Guide
13
4.2 Configuring the Analog Input
The AI configuration command structure is:
1200,n,ssl,ssh,sl,sh
1200: Command ID
n:
1, AI number
ssl:
Sensor scale low (Row value 0-4095)
ssh: Sensor scale high (Row value 0-4095)
sl:
User scale low
sh: User scale high
4.2.1 Clear AI Configuration
1210,n
1210: Command ID
n:
1, AI number
4.3 Configuring the SDI-12 channels
ADS-270 supports up to 8 channels.
The configuration command for a SDI-12 channel is:
1230,n,a,m,i
1230: Command ID
n:
Channel number (1-8)
a:
Sensor address
m:
Measurement set (0 for the aM! command, 1-9 for the aM1!
–aM9! commands)
i:
Parameter
ADS-270 addresses the SDI-12 sensors using the basic measurement starting
commands aM! (aMx!) and the D0!...D9! send data commands.
4.3.1 SDI-12 acquisition scheme
ADS-270 sends a start measurement command to the SDI-12 serial bus:
aMm
!
where,
a: sensor address
M: Start measurement command
m: void or 1-9, Measurement set (aM! or aM1! to aM9!)
This command tells the sensor
with address ‘a’ to take a measurement.
The sensor responds with:
atttn
where,
a: sensor address
ttt: the specified time, in seconds, until the sensor will have the measurement(s)
ready
n - the number of measurement values the sensor will make and return in one or
more subsequent D commands; n is a single digit integer with a range of 0 to 9
ADS-270 waits for either of two events to occur before issuing a D0 command:
1) receipt of a service request (a<CR><LF>) from the sensor
2) the specified time to elapse (ttt seconds)
ADS-270 issues one or more read commands (aD0! to aD9!) to read the
measurement parameters. Each parameter corresponds to one channel according to
the channel configurations:
