
OBS500 Smart Turbidity Meter with ClearSensor™ Technology
7.4 Communication Modes
7.4.1 SDI-12
The OBS500 uses an SDI-12-compatible hardware interface and supports a
subset of the SDI-12 commands. The most commonly used command is the
aM! command, issued by the datalogger. Here, a represents the sensor address
(0 to 9). The communication sequence begins with the datalogger waking the
sensor and issuing the aM! command. The sensor responds to the datalogger
indicating that two measurements will be ready within two (2) seconds.
Subsequent communications handle data reporting from the sensor to the
datalogger.
The SDI-12 protocol has the ability to support various measurement
commands. The OBS500 supports the commands that are listed in the TABLE
7-7.
TABLE 7-7. SDI-12 and RS-232 Measurement Commands
aC!
Measure
Close
ss (tu )
temperature (degc)
aC1!
Measure
Close
temperature (degc)
wet dry (0=dry 1=wet)
aC2!
Measure
Close
Send Data
ss (tu )
ratio (tu)
temperature (degc)
raw obs (volts)
raw ss (volts)
open current (ma)
close current (ma)
aC3!
Send Data
open wiper position count
open max current count
open timeout count
aC4!
Send Data
ss (tu )
temperature (degc)
aC5!
Send Data
temperature (degc)
aC6!
Send Data
ss (tu )
ratio (tu)
temperature (degc)
raw obs (volts)
raw ss (volts)
open current (ma)
close current (ma)
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