Campbell OBS500, Operator'S Manual

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OBS500 Smart Turbidity Meter with ClearSensor
®
Technology
18
7.3.3 Analog 0 to 5 Volt Wiring
TABLE 7-6. Analog 0-5 Volt Wiring
Color Description
CR6, CR800, CR850,
CR1000, CR3000, CR5000
Blue Shutter Open - Control High Control Port
White
Backscatter (Low) or
Sidescatter (High) Control
Control Port
Green Signal
Differential High or
Single-Ended Input
Brown Analog Ground
Differential Low or
Analog Ground
Black Power Ground G
Red Power SW12V
Clear Shield G
The measurement sequence is to raise the blue wire from ground to 5 volts to
open the shutter, delay 6 seconds, and then measure the backscatter analog
output on the green wire. If sidescatter is desired, then raise the white wire
from ground to 5 volts, delay 3 seconds, and then measure the sidescatter
analog output on the green wire. In either case, lower the blue wire to ground
to close the shutter. Note that measurements can be differential or single-
ended. Differential measurements are recommended.
The output is scaled as 1 mV per TU. For example, 100 mV = 100 TU, 4000 mV =
4000 TU.
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. TABLE 7-7 provides the commands available for the OBS500
operating system (OS) version 2 or higher.
If you have OS version 1, see Appendix D , SDI-12 and RS-232
Measurement Commands for OS Version 1
(p. D-1)
. Use the aI! SDI-
12 command or use DevConfig to see the OS version downloaded
to your OBS500. The OS version can be updated by using
DevConfig .
NOTE