Campbell Scientific OBS500 Smart Turbidity Meter with ClearSensor Technology - Manual (Page 29)

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
Commands Process Values Returned
aM!
aC!
a = address
Open Wiper
Measure
Close
Send Data
obs (tu)
ss (tu )
temperature (degc)
wet dry (0=dry 1=wet)
aM1!
aC1!
Open Wiper
Measure
Close
Send Data
ratio (tu)
temperature (degc)
wet dry (0=dry 1=wet)
aM2!
aC2!
Open Wiper
Measure
Close
Send Data
obs (tu)
ss (tu )
ratio (tu)
temperature (degc)
raw obs (volts)
raw ss (volts)
open current (ma)
close current (ma)
wet dry (0=dry 1=wet)
aM3!
aC3!
Open Wiper
Send Data
open wiper position count
open max current count
open timeout count
open current (ma)
aM4!
aC4!
Measure
Send Data
obs (tu)
ss (tu )
temperature (degc)
wet dry (0=dry 1=wet)
aM5!
aC5!
Measure
Send Data
ratio (tu)
temperature (degc)
wet dry (0=dry 1=wet)
aM6!
aC6!
Measure
Send Data
obs (tu)
ss (tu )
ratio (tu)
temperature (degc)
raw obs (volts)
raw ss (volts)
open current (ma)
close current (ma)
wet dry (0=dry 1=wet)
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